I've been a fan of Geoff's GP games ever since I bought Microprose Grand Prix on my old Amiga 600. I can't comment on F1C because I've never played it, but I've always been under the impression that Geoff's games were built on physics first, graphics second.
And, I've heard more than one TV interview where people have described real F1 cars handling like they're "on rails". Exact wording.
But I've never driven one, and I doubt anyone here has either, so who can say.
Bottom line for me, with a wheel, pedals, and all the driving aids (except gears) turned off, GP4 feels solid and very drivable. If I spin off the track, I know it's because I screwed up, and not some physics anomaly.
I've been waiting a good few years for another decent racing game to come out, but nothing yet has compared to GP4 or GPL. For online racing I generally play Toca2 actually, it's a good laugh