They really aren't similar at all though. Have you really played F1 2010? The physics aren't even remotely similar to anything codemasters has done before, especially not Grid. F1 actually has pretty damn realistic physics, not perfect but some of the absolute best on consoles besides GT5, race pro, ferrari challenge and it's clones. It leaves forza 4 in the dust (not that that is saying much, but people generally compare console "sims" to forza)
THe only codies title to have F1s other than f1 2010-11 was in TOCA 3, and even with pro physics in TOCA 3, the physics in F1 10/11 are just so much more realistic than that. If you compare all the GT cars in TOCA 3 to grid, you'll find that toca's pro physics are more realistic than that, so I can't see how you could even compare F1 to Grid, it's really levels above it.
I hate to sound like a broken record but hasn't anybody else noticed how much faster cars are than they should be in Grid?
I like to call it fast forward, because not only do the cars accelerate faster than they can IRL, but they take corners as fast as F1 cars do when they are not F1 cars. Please watch this video as amusing proof of this:
http://www.youtube.com/watch?v=WJogamd_3fg
In F1 2010/11, if anything the cars aren't fast enough, which is why I can't understand how you could say F1 is even remotely similar to Grid