Most 200G+ tank owners will tell you that a sump is the way to go. I used to have only canisters (2 FX5's on my 210g), but a sump lets you put in so much more media and you can use a pump that's much, much stronger than any canister filter pump.
The only down side to having a sump only is that it just acts as a skimmer for the top of the water. All the craps will be stuck on the floor of your tank. That's why I have a sump for extra bio capacity, a strong powerhead to blow the turds away, and a FX5 in the other corner to catch them all. I think that way you have a good mix of top and bottom filtration and extra circulation/gas exchange in the tank too.