Only downside to the XP3 that a couple of friends and i have had is reduced flow after a bit.
I usually have to clean it out every 2 weeks to maintain the flow at maximum, otherwise i believe the flow would only be half of what it should be. But meh, cleaning out this filter is very simple and i dont mind.
I have heard good things about the eheim classic 2217, but it seems a bit oldschool for me and doesnt even come with quick disconnects, and i have heard the hosing is very short. The eheims sometimes dont get cleaned in 3 months and they still have very good flow vs the Rena. They also waste less electricity