i personally have a sea cyclone with no complaints. it really depends on you, some people love the sea cyclone, some hate it. same with the prizm. hth, but i like the sea cyclone personally.
Prizm is very loud. Sounds like a sucking straw. Personally, Ive been considering ditching mine just to find something silent.
Not sure which is silent though.
i used a prizm for 6months on a 29 and 75 gallon reef and it worked awesome. I had the new 18 impeller so I wasnt bothered by noise. And it was in my bedroom. It was tricky to get in going but once you figure it out the prizm is great.