Okay, probably more Zakus around, but I usually find Zaku names to be easier to remember (they are kinda like Panzer IV variants) and they usually get more exposure. Usually easier to distinguish between Zakus too, by looking at their head or eye visor or chest.
Meanwhile most of the Doms look the same to me. Gotta look at and under the skirt (heh) or 'socks' to tell the difference. Pauldrons also work for some of them (Rick Dom II). And I guess the weapons loadout too, but those are harder to remember.