Is the 2015 Subaru WRX STI worth the $8k premium over the WRX? And does it remain one of the most capable performance cars on the market, short of exotic-car compromises (and price tags)?

Those questions seemed straightforward enough. But after spending most of a day with the new STI, first over back roads in California's Monterey Peninsula, and then out for hot laps on Laguna Seca, we found that the key questions were more complex than that—more like, how does the WRX STI fit into the performance-car market today?

I'd put the WRX through the paces of familiar test roads just a week before heading to drive the new STI, and found it an edgier, more capable car for 2015. After testing them both, we think that the difference between the WRX's $27k base price and the STI Limited's nearly $41k+ fully optioned price is vast in today's market, while the differences aren't as profound as they used to be. Subaru’s more affordable take on performance will be the one that the vast majority of buyers will be happier with—even if they’d thought about putting the extra money down for an STI.

ALSO SEE: 2015 Subaru WRX, STI Models Priced: WRX Gets Big Value Boost

Awesome new WRX is a tough opening act

And let's face it, times have changed since the introduction of the WRX in 2001 and the WRX STI in 2004. And with the all-new WRX going in a somewhat edgier direction—with more power and a stiffer suspension—it's an increasingly tough opening act to follow for the STI.

Especially when, in this case, what Subaru's rolling out in the STI, at first blush, looks very familiar on a spec sheet. Versus last year's STI, it's the exact same 2.5-liter turbocharged, horizontally opposed ('boxer') four-cylinder engine, making 305 horsepower and 290 pound-feet of torque. It's mated to an improved six-speed manual gearbox, with the same six forward ratios. And power is delivered via what's essentially the same all-wheel drive system, with a Driver Control Center Differential (DCCD) bringing a helical limited-slip front differential and Torsen limited-slip rear diff.

The four-piston front discs are the same size as those of the last-generation STI, while the rear discs are slightly smaller (12.4 inches vs. 12.6 inches). Front and rear track remain exactly the same as last year's STI, too.

Don't forget, the WRX got a new 268-hp direct-injection boxer four this year; it also now has a six-speed manual (or a performance-tuned CVT that can mimic an eight-speed automatic if you want), as well as a simpler version of Subaru's all-wheel drive system that we've found, is still a hoot to drive—and, probably, cheaper to fix if something breaks. The new WRX engine actually gets more peak turbo boost than the STI (15.9 versus 14.7 psi). And the WRX weighs about 120 pounds less than the STI in their respective base forms. Weight, by the way, is only up two pounds over the 2014 STI, despite more safety equipment, more interior features, and a bolstered structure, while at the top of the line, the STI Limited gains 27 pounds, due to its power driver's seat and Harman/Kardon audio.

Still a definite step up...

What does the STI have over the WRX? In addition to the performance-oriented all-wheel drive system, you get a bigger Brembo brakes, a larger (18-inch) standard wheel size, hydraulic-assist steering with a quicker ratio (13:1 versus 15:1), and a revised (inverted front strut) suspension that's tuned even a step stiffer.

You of course get a lot of other extras, like leather and Alcantara (faux-suede) seating, dual-zone climate control, an improved center console, and LED headlamps and turn-signal mirrors; and these altogether help erase some of the price differential.

That said, more aggressive front and rear detailing, the well-placed rear wing, and especially the Launch Edition's gold wheels (and classic WR Blue Pearl paint) do altogether give the design more punch. The only aesthetic aspect of the STI that we have a harder time looking past is the excessive front overhang—and the rear styling is no more flattering here than in the WRX.

Climbing into the STI for our road drive, it was immediately apparent, in the first mile, that some things haven't changed; the STI still rides stiffly (more so than the WRX), and has a noisy interior. Taking on the challenging surfaces of Carmel Valley Road, the suspension conveyed plenty of busy and jittery over the worst kinds of uneven patchwork, and crashed hard over some potholes and especially rough bits. There's also a lot of simple road and tire roar, on nearly every road surface—way more than in other sharpened small performance cars such as the Ford Focus ST or Volkswagen GTI.

The din from underneath is a bit surprising, as Subaru has put a lot of attention into how the engine sounds from inside. It's joined the legions of sporty cars to offer an intake resonator that pipes pulses from the intake manifold (via a damper) into the cabin. Such a system, which seems right at home in the BRZ, smacks of too much boy-racer for a $40k car (there's no way to defeat it, and we like listening to the exhaust and turbo-whistle sounds more); but it's tuned to only add to the chorus of sounds at higher revs and when you're really pressing your right foot into it.

Wow, what steering. And a great gearbox.

On a curvy road, we quickly forgot about the road roar and jittery ride. If you can look past those awkwardly fast-and-furious elements, the STI is a hoot to drive, with a flexible powertrain, excellent steering, and more grip and poise than you might ever need or sanely tap into on dry (or damp) public roads. The steering here is way better than what you get in the WRX. Although the one very meaningful change is that the steering ratio for the STI has been shortened to 13:1 from 15:1 (2.5 , giving the hydraulic assist (yes, there's no EPS here) a nice, relaxed center, great weighting off-center, quick responsiveness, and more feel from the pavement than you'll find in nearly any other performance cars today.

The gearbox you get in the STI—a heavy-duty one, with a parallel-rod linkage (and a short-shift kit in the Launch Edition)—is a lot sweeter than what you have in the WRX’s lighter-duty gearbox and cable linkage. Engineers admitted that it’s considerably more expensive.

Just as with the WRX, and the STI’s predecessor, this is a car that you can simply get into and drive very, very rapidly. You easily gain confidence, and with the tremendous grip of the performance tires, and the poise of the all-wheel drive system, you lose track of exactly how quickly you’re moving down the road until you wonder why that Mustang (or BRZ) can’t keep up with you.

There are three performance modes and six driver-selectable differential locking settings for the center differential. On the road we drove mostly with Sport selected on the SI-Drive controller, the stability system on, and the diff in the middle, default mode. But as we headed out for some track time at Mazda Raceway Laguna Seca, all we needed to dial up the right attitude was to pull the differential toggle toward the minus side for more neutral behavior on dry surfaces, click the stability control system once for its low-intervention traction mode, and twist the SI-Drive controller to order up Sport Sharp (S#) mode, which sharpens throttle response and helps the turbo spool up quicker.

There, the STI showed its reason for being, and in its stock setup (except for racing pads, to hold up to a long day at the track), it demonstrated everything we'd loved about this package in the past—either gently neutralizing understeer under power or turning it into glorious, neutral slides; and minimizing its weight transfer, dive, and squat for no-surprises maneuverability, phenomenally good body control that's always a bit better than we hoped for. The S# mode makes throttle response more vivid, too, and combined with the very sharp turn-in, the STI felt hard-wired to inputs yet surprisingly forgiving on a demanding course.

Back on the pragmatic side, the STI earns some embarrassingly low fuel economy ratings, of 17 mpg city, 23 highway. While the WRX earns ratings of 19/25 (manual) or 21/28 (CVT), both require premium gasoline. We did, however, manage to average nearly 17 mpg on an extremely spirited dash on hilly, tightly curved back roads, making full use of available revs at times. And if you run in the SI-Drive's Intelligent (I) setting, the STI’s throttle is calibrated to be more aggressive at and just after tip-in versus the last-generation model—engineers found they could do it without affecting fuel economy, they said.

Priorities, priorities...

We're actually not at all envious of those who have to redo performance-car icons like the Subaru WRX STI. Do you move forward with the pace of the market, betting against a potential backlash but drawing new enthusiasts? Or do you hold to a tried-and-true formula, rallying new enthusiasts around a winning reputation?

And all the while, the hordes of vocal fanboys and existing owners who are pushing that latter outcome might or might not be those who would be actually buying a next-generation model. The STI is a powerful performance car—just a performance car that hasn't changed (or matured) much, for better or worse, while the market has changed quite a bit.

The 2004 Subaru Impreza STI made 300 hp and 300 lb-ft, had a six-speed manual transmission and driver-controlled center differential, had a curb weight under 3,300 pounds, could get to 60 mph in 4.6 seconds, and got 18/24 mpg. The new model makes 305 hp and 290 lb-ft, and while that torque is more accessible, the car weighs at least a hundred pounds more and has an official 0-60 time of 5.1 seconds (admittedly, a conservative figure).

While the performance-car landscape has been shifting, it feels like the STI has been held back, with Subaru uncertain of which way to go.

The answer to loyal Subaru enthusiasts is probably going to be that, yes, the STI, as it has all along, offers a well-coordinated series of upgrades to bring a distinct step up in performance.

But others—even this editor, who would consider himself a Subaru fan—it's not as straightforward of a decision. Unless you're wowing (or scaring) your passengers with this car's performance capabilities, they're more often than not going to take a look at the homely compact-sedan silhouette on the outside and more so, the hard-plastic door panels and somewhat thrifty interior and say: “This is a $40,000 car? Really?”

The other factor we can't ignore is that there's a lot of disappointment of the look of the WRX and STI. Enthusiasts expected a lot more visual differentiation from the Impreza—and products that were given a look more like that of the racy Subaru WRX concept Subaru had teased.

More competition this time around

The Volkswagen Golf R will start at or maybe just below the STI's bottom-line price of about $35k. Audi's S3 will land somewhere just above a loaded STI Limited. And the stunning Mercedes-Benz CLA45 AMG starts about ten grand more than a base STI. And there's the Ford Focus ST, which isn't as quick but is a lot cheaper and might be nearly as much fun.

Based on an early preview drive of the Golf R, we can already tell you that the VW, with the DSG gearbox, is going to be a far more refined and agreeable way to get around 300 horsepower kicking out all four wheels.

The compact-car performance landscape has just changed so much over the past several years. While the WRX remains a bargain, and we feel that Subaru has kept it in pace with the wants and needs of practical, value-minded performance buyers, it's increasingly difficult to say that the STI is a performance value, or a lust object beyond a narrowing cadre of enthusiasts.

Letting the market move on?

More than ten years ago, Subaru managed to bring the Gen-X end of the enthusiast market exactly the fast-and-furious car they craved, in the original WRX (or STI). But today, most of those enthusiasts have moved on, had kids, and are in their 40s, driving BMWs and Audis.

It's not that the WRX STI is an obsolete idea; it's that, given how great the current WRX is (and how Subaru's cleverly repositioned it and kept it relevant), the way the STI is priced and presented for the U.S. feels obsolete. Is it time for Subaru to change its formula and try to keep up with those tech-forward rivals—to consider things like continuous damping and active noise cancellation? A lap timer or race recorder?

If commute duty is part of it, there are plenty more enchanting options nowadays, especially considering the price. But if track time is a priority, the STI will put a grin on your face as well as it ever could.


Follow Motor Authority on Facebook and Twitter.