I'm pretty sure both are bad but Brachio has some more noticeable issues with its design so I'm picking the rhino

Brachio has the main issues of elephant feet, forehead nostrils, standing on hind legs, and being oversized.

I don't play JWA so idk how accurate that thing is, but it does look weird.

Could brachio kick like a horse though given its more developed forearms

Afaik, probably not a full blown bronco kick, no, and I doubt it'd be flexible enough to fully reach behind it like one either.

This is so sad