in the real world the Vspecs have different differentials to the nonvpec units, they're active rather than your regular lsd i think, but i don't know how much of a difference there in in the game. I think the R34s handle the best of the lot. the 32s have less weight but less grip and power when fully tuned, largely because they behave too much like a rwd when compared to the 34. rwd is still good, so they're still fast, the R34s are just easir to make go fast if you're hamfisted