I have a cascade 1000 on my turtle tank. It works pretty well in my opinion. I like the priming A LOT better than my Rena XP canisters. Some of the reviews say they are loud, I just put my ear up to both my XP3 and my cascade...no real difference that I can tell.
The main difference that I see is build quality and flexibility. The XP's simply feel rock solid and heavy. The Cascade I had actually came broken, but I got a free replacement part from bigals. The cascade is made out of very light plastic. There is also a bit more flexibility in how you want to hook up the inlets and outlets on the XP's. Hard to explain without a picture, but I found it very difficult to set this up for a turtle tank. The inlet tube was a fixed length, no add on tubes to put the inlet lower in the water. The outlet was too high up in the tank and basically made a waterfall in my bedroom. I had to do a lot of modifying to get it to work for a turtle tank, but it would be perfect for a tank that is actually filled to the top.
Would I buy it again? Sure, if I can get it for half the price of any other canister. It works, it filters, what more can you ask? haha