I think the armor from AvP Extinction (the military Hydra and Blazer classes) looked like true armor, nearly impenetrable. I think we just need to see the creatures in the right circumstance for the extra armor to make sense.
Light armor represents minimal protection, maximum flexibility and agility. Heavy is the opposite. I would consider the armor in the AVP films to be more of a medium style, as they did some impressive jumps that I think they would have had trouble had they been wearing a full body suit.
The pictures posted are really nice and I would love to see feature in a film, regardless of body style (fit vs. bulky).