Well, my first big car in GT4 was the S7. I sold it after I got done dealing with understeer and poor accel (this was when I was a noob and didn't know anything about gear ratios :]).
I am quite a fan of the GT, but lately I have not been able to keep control of the thing. I am not sure why. I have 4 of them, 1 fully tuned, one fully stock, one I bought especially for Nurb, and one I use for the appropriate races.
Otherwise, it is a very, very solid car. I like the look. And for those who say the GT has bad, unoriginal looks, it is modeled after the original GT40 from 1969.
And for the Zonda, I have actually very recently sparked an interest in the funky looking car. I did a comparison on the 1/4 mile and it did the best out of the 3 in stock with N2 tires. I like it the best as of now out of the 3.
And by the way, I am pretty sure the Ford GT comes with racing tires stock; just throwing that out there.