In my opinion they are two different types of keeper:
Cisak is more of an acrobatic keeper, likes to dive around and parry rather than hold the ball and takes risks sometimes. His kicking and reading of opposing players is exceptional, he also has great reflexes (That save against Bradford was phenomenal
) He communicates well with his defense. The only issue has have found with Cisak sometimes is his positioning, he comes for a ball sometimes that he doesn't need to collect.
Bouzanis however is more of a traditional keeper, strong in the air and likes to make a stop. Although, Bouzanis to me didn't display the leadership qualities with his defense like Cisak does. I also don't think he had the confidence in himself to take risks the way Cisak does. (To be fair, the form Cisak has been in he must feel top of the world right now)
I still think Bouzanis is a quality keeper and defiantly has talent to be better than Cisak IMO but lets be fair sitting on the bench at Liverpool all season has done him no good. He really needs to go on loan elsewhere again and become more experienced. Till then and probably for a long time Cisak gets my vote without a doubt.