Never heard of Proquatics, (or have and just can't remember) So I will have to go with the Emperor. I have a Emperor 400 on my 55 and it wokd wonderfully.
i'm sure that no one cares because no one ever listens to me anyways but the best hob on these lines is the penguin 330.it's better than the emperor because it doesn't have nearly as many moving parts.less moving parts is better.the proquatic looks like a nice filter and there was a member here that loved his but he hasn't been around in a while
I have a proaquatics filter in my 10G...so its not nearly as big as the one you're looking into, but its a cool design. The bigger versions even moreso than my little version with extra chambers for media etc.