So I've been looking into getting a new large canister, and I was looking at the eheim pro3's, then I look at the price, and the flow rate. I know flow rate isn't everything, but other than media capacity, which I frankly feel is a little over rated, especially since I clean my filters at least once a month, why would I get a pro3 for twice the cost of something like an xp3 or xp4?