Without a doubt your lap times are quicker in a faster car, but my opinion is based on that ive done a 10 minute lap on totally the wrong line in a 350bhp saph when I first went, and its nowhere near as rewarding IMHO as a ten minute lap in a standard 1.4 corsa would be.

I think we probably all agree that if you want to be doing lap times you need all of:
The lines
Some driving talent
Commitmant
A car that handles / brakes / accelerates



I just feel that the order I listed them in is the order of importance, so im personally going to concentrate on the lines on my next trip, and then maybe the trip after I will take something fairly quick and see if I can get a "respectable" lap time.