Logic Pro needs an update for the 2010 macs. It doesn't handle 6 cores properly. You can install dev tools to disable 2 cores so it runs faster until a patch comes out.
It should be fine on the 4 and 8 cores (although the 8 doesn't support the hyperthreading cores yet). The 6 doesn't work right and performs better if you turn off two of the cores (making it a quad). I haven't seen any reports on the 12 core.
I'm sure if you upgraded from a really old, slow machine, the hex is working way better than that. But it is still working worse than a quad, I wouldn't call that "great" especially for that price.