I believe some of the car manufacturers, even have different types of AWD systems in their line of cars. For example, the Audi TT has a different (cheaper, and not as good) one then you'd find in their 4 series.

 

The TT / A3 used the Haldex system. It's good, but not quite the performer as the Torsen.

 

This is really a very open ended question. There are several general types of AWD/4WD systems and lots of subtle variations that can make two similar systems drive differently. Also, when you evaluate a system in a car you have to remember that you can

 

What about Nissan's ATTESA ETS system, made famous by the GTR? G35X's seem to be really popular up here in the NorthEast.

Here is a nice R&T comparo for AWD system.
http://www.roadandtrack.com/article.asp?se...article_id=3280

And here is the article for the G35x (older model)

http://www.roadandtrack.com/article.asp?se...0&page_number=3

The Infiniti only comes in 6th here, but it's my favorite due to the RWD oriented nature of the ATTESA ETS system, which is known for kicking into AWD only to save your butt. You can have power oversteer, sharper responses, etc. It'll keep your wife safe, and yourself happy. And the new G35 fixes alot of the old G35's rough edges. What impresses me the most about an AWD system is if can really improve upon the RWD car. In the case of the G35, it does, despite the added weight (which is probably why the GT-R's had it all along).

"Rear Drive vs. All-Wheel Drive: That Is the Question

For fun, we brought a rear-drive Infiniti G35 to our autocross and compared it with its all-wheel-drive G35x brother, in both wet and dry conditions with VDC yaw control switched off. We assumed the rear-driver would be quicker in the dry, given its ability to hang out its tail and help the driver tighten his line. But in the wet, we were confident the all-wheel-driver would have a tremendous advantage, hooking up better out of turns. Here's what we learned:

Well, we were wrong on one front, right on the other. Based on group average times on the dry autocross, the awd G35x proved itself faster, surprising us with its rear-biased manners and lapping nearly a second (0.9 sec.) quicker than the rear-drive G35. In the wet the G35x fared even better, 1.3 sec. quicker than the rear-drive G35.

Credit goes to the electronically controlled awd system, which maintains a rear-drive bias while endowing the car with improved stability. Don't get us wrong, the G35x still liked to hang its tail out, but the driver didn't need to be quite so careful with the throttle to keep the car's back end in check. In the rear-drive G35, the driver had to be far less aggressive with the throttle (and quicker with corrections) to post respectable times. Wet or dry, the awd G35x was far easier to drive quickly.

The G35x's center diff is responsible. From 0 to 10 mph, its electromagnetic wet clutch splits the torque 25 percent front/75 percent rear for good grip off the line; thereafter, the car is 100-percent rear drive until rear-wheel slip is sensed. Then, the diff can send as much as 50 percent of the power forward. Although other awd systems will produce different results, the G35x proves that all-wheel drive, properly applied, can give you the best of both worlds.