I guess it depends on how cleverly shaded the LFS skin is.
They're claiming the polycount in FM3 is around a million per car (presumably that's in photo mode, no way it could run that in full race mode) so obviously a car with curves is going to look way better than anything in LFS
But with clever skinning you can give the appearance of curves and lines that aren't really there.
They wouldn't stand up side by side though.