Cant really compare them because they are 2 totally different styles of game-play, exit path is survival/racing and colony is strategy, but if i really had to pick one I'd say exit path because I'm pretty bad at strategy games, still both really good games though.
Colony's riddled with hackers these days, but I still have to love the game, especially 2v2s. The teamwork it takes makes things interesting. On the other hand, Exitpath has a better "Uniplayer", and more cool touches (such as flair, acheivments, etc.). Personally, I would have to call Colony the better game (though I like them both), especially if you're looking for multiplayer.