I think it's pretty clear that the East is more top heavy, but the West is far deeper. Which one is "tougher" depends on what kind of team you are. If you are a CFP contender type, you'd rather be in the West, where there are no other teams that should be at your level; if you are a team just trying to get bowl eligible, it's probably easier in the East, where you get more "should win" type games.