Hi,
Here's my "personal opinion" about both games. Been playing F1C for about a week now to give it a fair chance against GP4, which most of us has peen playing for years.
F1 Challenge
pros:
Good Graphics(specially individual cockpit per team)
Good Sound
Great Force Feedback!( this is a big plus, I wish GP4 has FFB this good)
cons:
Extremely Stupid AI (Imagine Schumacher always on pole and then always gets off the track in the first corner)
Poor Reply (Car movements seem unreal)
No mid race save game
Bad Tracks
Compared to GP4.... GP4 has
Far Better Tracks
Very Realistic AI
Great Replay
Good Graphics as well
Good Save game system(you can save the game at any point of the race)
For "Me" GP4 only looses out on FFB and Sound.
I'm never gonna play F1C again. Stupid AI simply makes me loose interest in it as I always play offline. I think F1c would have great racing only if your playing online with some friends.
What also discourages me is F1C's save system. You can't save a game mid race. I always play 100% race to really get that F1 feel, but most of the time, I dont have time to play 1h:45min straight. So I save it mid race in GP4. This you cannot do in F1C.
Community, GP4 has much better and far more active community of fans and modders. This is wht gives GP4 a very long lasting appeal.
Last, is Physics. I will not give any opinion about this. I am really not sure which is more realistic. The closest I have been to real racing was Old School Drag racing with with 160hp N/A cars and European style Kart Racing. I will leave the physics judgement to those who has real formula car experience.
No arguments please, again, this is only "My Personal Opinion"