In general, it seems to me (from my limited, non-professional experience with earlier versions of both, on the wintel platform) that Maya is more powerful, but can be more confusing to learn at first (some of the key combinations are plainly odd). 3dsmax seems to be geared more toward those who make game models and stuff, while Maya seems to be better to use for more realistic renderings (of course, neither are limited to one or the other kind of work; this is just my subjective opinion on which is easier to use for what).