I am a big fan of both games, and have been switching back in forth between the two in the last few weeks. I haven't yet driven the GT5 F10, but if it's anything like the F1 cars of past GT games, then I'd have to go with F1:2010 being more realistic. I attended Skip Barber Racing School to learn open wheel racing, and the F1:2010 cars are about as realistic as it gets for a simulation. The lack of turning while braking is very real, which is why it's so important to know every turn in and out. F1: 2010 requires so much more work to win races, and even though winning doesn't get you rewards or new cars, I feel much more rewarded for taking 1st place. I just wish GT5 offered a little more competition. Even the F1: 2010 AI is better, they actually avoid crashing into you, unlike GT5 where they'll pit manuever you right off the track.