Well let see...Last week I drove the following cars, all in the same day.
Stage 3 S4
Stage 3 A4 1.8t
Porsche Boxter S
M5
my Passat (stage 300.000 BTW)
All the cars are very different, and react different too. Despite 3 of the 5 being turbocharged, and VAG products. Honestly I was most confident in my car, I know it and I have perfected (well IMHO) how to drive it. The M5 is the most diffacullt for me to drive, because it is NA, RWD, and heavy. But it is a great car.
Long story short - to know what your car is going to do you have to push it to it's limit (in a safe environment like a track). Then you can learn how to get it to do what you want it to, and what it simply will not do.
This only makes to closing of all the local tracks, a greater loss. I will be going to a track at some point this summer, I too, still have lots to learn.