Another Humanized MLP - FiM wallpaper from me, featuring Celestia and Luna , and as usual I designed weapons and all just for some decoration and my obsession of adventure fantasy theme.
I'd imagine Luna as being a bit more of a flamboyant fighter, and it's hard to be one with a lot of armor, while Celestia would more likely be efficient in her fighting, thus allowing for more armor.
I like how Luna has lighter armor than Celestia, or at least appears to be so since her skirt and cape aren't as bulky. I can see how the regular populace would view her as dark though, especially when Celestia looks more like a paladin.