P1 + Celtic + Gort all have the curious look..
Mr. Black + Wolf + P2 all have the more aggressive look.
Interestingly enough, the Boar brothers and Chopper seem totally lifeless. Kind of interesting you'd point out the emotion behind those other designs, because it brings to mind a good way of judging a helmet. A bio can be a good design if the viewer feels and responds to whatever vibe it gives off. Plus, the helmeted look is what we see most of the time, so it's gotta be good.