I have Rena XPs, Marineland C series and a couple of others. My opinion is simple, I just got a new XP2 for my used 55 that I picked up off craigs list. The basket system is a pleasure to work with, it is self priming and it is very quiet. My oldest one is about 4 years now bwcause that is when I got back into aquariums. The C series is a decent filter but is manual primed, takes perfect alignment to reassemble and the shutoffs on it only worked for a few months. Now when I clean it I need to hang the hoses up on the tank to keep the tank from siphoning itself empty through the hoses. It does prime easily but I like to just sit an empty filter housing in place and open the hose connection head like I do with my Rena. Why would I want to struggle with a priming pump for no reason?