I say this because I really don't feel any different playing one side vs. the other. When both sides look like creepy saurus catipult creatures and fat men on walking chairs, I feel like I'm evil no matter which side I play. However if the light side could get different 'lighter' models, even if their stats were exactly the same it would make it really feel like right vs. dark, rather than just two random groups of the exact same people.
It was pointed out to me when I voiced this among others that DotA had different units on both sides, which did make them feel different.
Suggestions I brought up were:
Instead of minotaurs, the light side could have golems
instead of archers, the dark side could have salamanders (or some sort of spitting lizardman)
instead of priests, the dark side could have hierophants
Instead of catapultasaurus, the light side could have strange monkey things that spin their arms around to throw boulders
instead of angels, the dark side could have devils
Instead of giants, the light side could have behemoths