THE INFINITI I30 and Nissan Maxima are twins separated at birth. The difference is that the I30 grew up in a better neighborhood. Here, then, is a description of how environment influences outcome.

The 1996 I30 looks better than the 1995 Maxima, even though they share an identical platform -- the automotive equivalent of DNA. I have a theory about why the I30 is more attractive.

If you grow up wearing nice-looking clothes, you tend to think better of yourself. If you think better of yourself, you feel better. If you feel better, you smile more often, which makes you look better.

The I30 grew up wearing nice-looking clothes. It has a fancy "waterfall" grille that puts the face of the Maxima to shame. It has a more attractively outfitted rear end, fancier wheels and a plush interior. The I30 looks rich.

The Maxima, on the other hand, looks very middle, very suburban. You drive it to back-yard cookouts. You drive the I30 to the country club.

There's also the matter of upbringing. The Maxima can be found at Nissan stores, along with lesser Nissans, such as the Sentra and the Altima. The I30 can be found at Infiniti stores, which are replete with luxury appointments and well-dressed salespeople who bow and scrape at your every wish. The Nissan stores often are crowded so-so places where salespeople may or may not acknowledge your presence.

Have you ever been around people who grew up with servants? They have a certain air about them. Hell, you almost feel like doing things for them, even though you know better. Well, the I30 is like that. Lots of folks know that it's related to the Maxima. But the I30 gets far better treatment at restaurants and hotels than the Maxima. Valet parking dudes fight to drive the I30, but they leave you to park the Maxima yourself. Life ain't fair.

Background: Sad story, really. The Maxima and I30 were separated at birth by cruel marketing masters who sent one to Nissan and theother to Nissan's luxury group, Infiniti.

The Maxima rose to the top of the Nissan class, but, alas, it was the middle class. The I30 rose to the lower-middle portion of the Infiniti class, holding a station between the Infiniti G20 and J30. It didn't matter, because Infiniti is the upper class.

Mechanically, there's not a whit of difference between the I30 and the Maxima SE. They both come with 3-liter, 24-valve V-6 engines rated 190 horsepower at 5,600 rpm. Maximum torque is 205 pound-feet at 4,000 rpm. Dual front air bags are standard, as are power four-wheel-disc brakes with anti-lock backup.

The I30 can be equipped with either a four-speed automatic transmission or a five-speed manual, same as the Maxima. Both cars are front-engine, front-wheel-drive sedans that can carry five passengers and 14.1 cubic feet of luggage.

The I30's decorative trim lines include Standard, Luxury and Touring. The Maxima's trim lines include a base GXE, a sporty SE and the luxury GLE.

Complaints: None, really. The I30 takes care of my basic gripe with the Maxima -- appearance.

Praise: Both the I30 and Maxima are exceptionally well-crafted, enjoyable cars. I'd be happy with either one on the open highway.

Head-turning quotient: The I30 has more "Yo!"-power than the Maxima.

Ride, acceleration and handling: A triumvirate of performance excellence in both the I30 and Maxima. Braking was excellent.

Mileage: In the tested I30 Luxury, about 23 miles per gallon (18.5-gallon tank, estimated 410-mile range on usable volume of recommended premium unleaded), mostly highway, running with two occupants and light cargo.

Sound system: The I30's standard system includes a six-speaker, 200-watt Bose AM/FM stereo radio and cassette with compact disc. Bodacious boogie! The same system is optional on the Maxima; a four-speaker, AM/FM stereo radio and cassette is standard for Maxima.

Price: The Infiniti I30 was released May 14, so the price isn't set yet. The tested I30 Luxury model will cost an estimated $32,000, roughly $2,500 to $3,000 more than you'd pay for a fully loaded Maxima SE.

Purse-strings notes: Your call. You wanna be fancy? Get the I30. You just wanna have fun? Get the Maxima.