SOMEDAY AN AUTOMAKER will introduce a car called the MLC, for Midlife Crisis. It will be for racers who grew up but didn't grow old.

For now those racers can be satisfied with the Audi A5, one of the latest entrants in the increasingly crowded category of luxury coupes. The A5 is stylish, quick and a whole lot of fun to drive. It's also an illustration of Audi's effort to provide performance comparable with that of BMW's cars but with more style and creature comforts. And jokes about midlife crises aside, luxury carmakers such as Audi and Infiniti are hoping their sports cars will be fresh enough to keep boomers on board, even in an economic slowdown. So far, so good: Infiniti says sales of its G37 coupe are going strong, and Audi says the A5 is one of its hottest sellers.

We recently compared the A5 with the G37, the luxury version of the famed Nissan Z-car roadster. The A5 started with some disadvantages. Its base sticker price of $41,975 (including destination charge) is about $5,000 higher than the manual transmission version of the G37, a difference that can grow when you add options. Then there's the horsepower gap. The G37 boasts 330 horses, versus the A5's 265. This should be no contest, right?

Wrong. Despite the G37's strengths, the A5 is simply a more appealing car. Its agility, refinement, better-quality interior and curvy-muscular styling offset the G37's extra horsepower. The A5's only comparative drawback is the price though, to be fair, the A5 comes with standard all-wheel drive, while the G37 is rear-wheel only.

The more interesting question is whether any high-horsepower luxury coupe makes sense these days, when Wall Street bankers are getting pink slips and premium gas has reached $4 a gallon. On the plus side, both get decent fuel economy (about 20 mpg combined city and highway), especially considering their performance. Just don't drive them to the local Sierra Club meeting.

Audi A5 The A5 we tested carried a sticker price of $52,140. It included a six-speed automatic transmission that allows for clutchless manual shifting, plus a bunch of special-options packages. We would take the six-speed manual transmission instead of the automatic. We usually prefer to pick and choose features without buying an entire package. But we like the $1,850 premium package, which includes heated front seats, and the $1,700 technology package, which has the best rear-vision parking system we've seen. But dispense with the $2,900 sport package. The 19-inch wheels are cool but less tolerant of potholes than the standard 18-inch wheels.

Audi says the A5, with a manual transmission, goes from zero to 60 mph in 5.8 seconds. It also handles remarkably well it's tight without being jumpy and the interior is fantastic. The instrument panel has a clean, uncluttered look; the seats are comfortable and supportive; and the interior plastic has a high-quality feel that is soft yet firm.

Infiniti G37 Coupe We tested the top-of-line G37 Sport 6 MT (as in six-speed manual transmission) with a sticker price of $43,365, making it nearly $8,800 less than the A5 we drove. Only five-speed automatics are available on the two other versions of the G37 coupe. Edmunds.com says the G37 goes from zero to 60 in 5.4 seconds, a bit faster than the Audi.

Options on our G37 Sport included the $1,150 technology package (precrash seat belts, adaptive headlights, etc.), the $3,200 premium package (power moonroof, heated seats and more) and the $2,200 navigation package (dashboard navigator, rear-vision camera for backing up and so on). The G37 Sport has a sport-tuned suspension that lets you feel the road and comes with 19-inch wheels, instead of the 18-inchers on lower-priced models. Hard-core enthusiasts will appreciate both, but we found the car a little jittery, especially on bumpy roads and wet pavement.

Infiniti's interiors are much improved from a few years ago but remain a cut or two below Audi's. The cupholder doesn't hold tall drinks very well, and the seats seem snug even for someone of average build. The exterior styling is attractive but not eye-grabbing. Bottom line: The G37 coupe offers more horsepower for less money than you'll pay for other cars in this class, but it sometimes feels more raw than refined.

For more SmartMoney Magazine features, turn to the October issue .