It seems that each empire follows a kind of "style" if you will. We already know it, but I'm just putting it into words.
Terran Republic - Seems to have a very "rounded" style. Their armors do not seem to have sharp edges as much as the other ones. Their MAX is a good example, with rounded shoulders and a sphereical head-protector-thing (not really a visor, not really a helmet). Other than being "round" you can't really classify what kind of style it is. It just is.
Philosopher's Whim: This could mean that since they've been around for so long, they're adaptable. They roll with punches. If something happens, they adjust. I mean... they'd have to be if they've been around for over a thousand years...
New Conglomerate - Have very blocky and sharp edged armor. Very definite. Some compare them to legos. I tend to think of them as more of an industrial type of armor. Even some their weapons seems to reflect this (i.e. MAG-Cutter - I mean LOOK at it for cripes sake! How can you not call that an industry's standard issue cutting knife?). While the actual armors are not cubical in design, it is definitely "blocky" nonetheless.
Philosopher's Whim: Having the armor with such precission could mean that their ideals and goals are exact. They are idealists, and in being such, cannot accept anything less than the ideal they are fighting for. Thus, the sharp edges and overall blocky look of their armors.
Vanu Sovereignty - The general futuristic style approach. While not easily described, it is (nonetheless) a style. They have a kind of elongated scale style in most of their designs. Much like that of a lizard or other reptile. They also seem have "beefier" shoulders in most of the heavier armors. The medium type reminds me of a japanese samurai warrior (even though it's probably my imagination) and the MAX seems to have a very Samus Aran feel. If you've played any of the Metroid games, you'd know what I mean.
Philosopher's Whim: Nothing too deep here. Their armor is futuristic. Why? Because they are the Vanu, n00bs.
And yet... it seems their armor does posses some kind of organic feel (as it was mentioned by someone else). Maybe the "scales"? If so, it could be interrpreted as meaning the Vany have a kind of collective goal. More of an inhuman approach to this war then the other two factions.
I just wanted to make this observation... and a poll. That's really the only reason, now that I think about it. The poll.