Ya, I've had races where I would win by a landslide only to have someone else take first place winnings... drives me nuts. Sad thing is, the times are the same just the finishing places are different. I've had winning times of around 7:15ish to be "beat" by times of over 7:40... explanation: the track marshals are drunk!!!
As for the cars, I haven't noticed any real difference tbh. One possible explanation for your Audi being a bit more stable could be you were in a room where SRF was on. You can't change it because it's "greyed" out... most rooms it says it's off, while in some rooms it says it's on.
You can see that when you adjust your settings. (ABS, TC. etc etc)
Cheers