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
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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.