It really depends on your skill level I guess.
Sometimes though, slow IS faster. You will usually find more difficult to find a consistant lap time with a car thats too fast.
I am too used to stock now to try anything quicker, but I know your reactions need to sharpen up the quicker you go.
with a slower car, your braking points change, or do not exist, hence why some people like a one way with a slower car, to keep as much off power speed as possible.
try using a one with with a mod.... and you will wish you hadn't!