Quoted from T7:IM has better software, which makes it a better game.
ST has deeper software - but that's not the key to better software. All the modes still feel rather the same in ST from a playing standpoint. Sure the graphics are different, but who cares? I'm not watching the DMD much while playing the modes.
I have both, and like both - but IM definitely gets more playtime from both myself and friends (except for a few really into Star Trek movies)
+1