The A600 has some sweet new accelerators in the pipeline, which may or may not make it to the A500, if/when they're released/finalized. Other than that, they're both very customizable (for the right amount of $$). Six of one, half dozen of another. Only dealbreaker? No numeric keypad on the A600. Personally that's a big deal for me (and I know some games require it). But again, others couldn't care less.
