Any preferences over the 599 or the Enzo; will probably tune both up although heard they both love to understeer on turn in. I'm also tempted just to save up and go for Formula GT or the Pug 908...
I have the 599 and it handles really well, not as good as my F430, but I think it's me and the extra power disagreeing rather than the car. People who say 599 understeers need to learn to break properly, the car goes quickly, you need to break earlier than in the Fiat 500.
The enzo is probably quicker, but I just love the way the 599 drives, i've driven one in real life on a track, it was mind blowing and I'd say the handling in game is very close to the real thing.
The Enzo is the better car in terms of speed and handling, but both are fun cars. The 599 is very fast and handles quite well considering its weight and layout. If you're focusing entirely on game progression than listen to other fine folks and save for a formula GT. If you have your heart set on a Ferrari you want to consider the F430 Scuderia or the 458, both are amazing and about as fast as the Enzo (stock that is, I don't tend to tune my cars so I can't comment on how they are maxxed out).
599. I was smashing races stock that my friend couldn't complete with his tuned 458. The Enzo isn't as great as it should be in this game but the 599 exceeds expectations, it's a hidden gem.
thanks for the input, I already have a Scud that I couldn't want much more from. 599 is starting to sound more tempting, I was really hoping the GTO might have founds it's way into GT5 :|