One thing is certainly true on GT5 compared to real life..
Kick the back end out on a RR or MR, and you will NOT recover easily unless you are a driving God. Of course, the back comes out less with the added grip over the rear wheels...
FR cars tend to handle the "Best", as the weight of the engine rests on the front axle (Or near it), making sure the front wheels are touching the ground as much as possible. This is preferred, as more contact=more grip. The disadvantage usually comes when you mash the throttle in the footwell as hard as possible, and because there is less weight over the back, your rear slips out (Oversteer). This is typically the "Easiest" way to drift.
FF cars understeer slightly, for reasons which in my head contradict themselves. I'll report back when I've solved why. Im sure it has something to do with the differential.
MR Cars tend to be quite "Stable", in terms of front and rear grip. The thing is, however, that most MR cars are quite powerful, so the tail will still get a bit wayward. It's more difficult to correct, because there is more weight at the part that is swinging. For instance, if you try to spin a piece of string with nothing on the end, it's easy to stop. If you spin a string with a weight at the end (Key, rock, ball) its harder to stop, because the momentum is greater. Usually, if a MR car gets bent out of shape, the tail is swinging so hard that even with your best efforts, your car will spin with it, and you will be backwards, or in a wall. Additionally, a small side-effect with having an MR car is less weight over the front wheels, causing much less front-end grip, and thus, less actual turning power. This is why MR Racing cars (Formula 1, Ferrari's, Zonda's, LMP's, etc) have front wings, meaning the grip is regained through downforce. For instance, the Ferrari F10 handles quite nicely, it has a big front wing, and is MR. Meanwhile, the Ferrari Enzo has no front aero grip, and is also MR. The lack of any type of front grip results in hideous cornering capability, which is only solved by braking VERY early, or setting up the suspension so stiff at the rear, and so low at the front and high at the rear that it 1. Looks stupid and 2. Really becomes stupidly unstable.
RR Cars are like MR, only worse. Even less rear grip, and theres even more weight over the part that has no lateral control- the rear. The advantage to this is- Assume there are 2 cars
Porsche 911 (RR)
BMW M3 (FR)
Assuming they have the same power, and weight, the Porsche will murder the BMW in a drag race because it has so much more rear grip, and more rear grip means more tyre contact, and more rear tyre contact means more of the horsepower is being put to the road, which helps aid in Straight-line speed. Additionally, with a good differential set-up, the Porsche will be less likely to oversteer, because the rear tyres are glued to the track. But, because the Rear tyres are so grippy, this results in a loss of front end grip which means either
A. You will understeer into a wall, causing you to crash, curse, get back on track, get slammed by the careless AI, and then hit another wall, curse more, and eventually restart the race.
-OR-
B. You will get so fed up with the lack of turning, that you will nail the throttle to the floor, and you will eventually spin the rear wheels, resulting in an "uncontrollable" oversteer, which will also cause you to hit a wall. Again, with a good Diff and Suspension set up, this can be avoided, but not totally prevented.
AWD cars are somewhat interesting...
Because all 4 wheels are being powered, this results in monumental amounts of grip off the line, virtually eliminating wheels spin. But, when you come to a turn, in a FR car, the front wheels spin at different speeds because they are traveling different distances around the corner. But, in a AWD car, both front wheels are traveling at the same speed, and this will usually result in some kind of understeer. IF the AWD in GT5 was fully independent, these cars would rock, but sadly, they arent. With a good diff set-up, you can help this to some extent, but then you risk spinning one of the front wheels, resulting in an overall loss in front grip. But AWD cars live and die based on the type of car they are, and how they are tuned... The Audi R8 is a wonderful AWD car to drive, it's secure, and still quite good in the corners. But, you'll find you can take corners much faster if you coast through them, but that will reduce your grip under braking... its very complex. In most situations it's more "Safe", but a bit slower than a MR or FR.
In all honesty, it depends on your driving style... If you like to get perfect lines in a corner, and use all the rear grip for maximum power, then a MR or RR or AWD would be good for ya. But, if you want security in your ability to correct a drift, at risk of drifing more than in the other types, a FR is good.
) if turned more, 50% throttle and so on. for ff, it was opposite and produces understeer when it was floored, and thats all i know bc i rly havent driven one that much. 
