I have the stealth and several standard F1's in different states of tune and IMO I find the stealth with the extra front and rear downforce will own the standard version on all but Le-sarthe, it corners far better once set up correctly and rips the standard to pieces round the ring, Also I find out of all the different F1's I have the highest bhp can become a tad to overpowered and do prefure mine to run around 750 bhp. But hey we all have our own styles and that will show with these cars.
F1 IMO is the best road car in the game and a joy when you have it setup correctly.
Edit : To all stealth owners search for Avid tuning, he does a tune for the F1 stealth thats very good, you may only need to tweek it to your style of driving.
Then practice,practice and practice and when your ready go online at nurburgring and own everyone.