Wouldn't it be boring if it was a 1 sided battle actually?
Well, there aren't much benefit to being either way, in an attempt to let people truely decide their allegiance based on personal preference the custom gears for light give the same bonus as their dark counterparts, and quests are similar (not 100% the same), if we made either side too easy or too strong, it would become unbalanced and people would choose their allegiance for the wrong reasons.