@chad590, both will work.
It just depends on how much flow you want in your tank.
But remember, the rated canister flow will be greatly reduced due to prefilter mesh/sponge intakes, filter media, chiller, and spraybars. So a 206gph rating of the Fluval 206, might actually only be 160gph.
So if you thought that 206gph was a lot of water movement, it isn't after it's installed in the loop.
In regards to choosing a canister filter, I would personally choose the bigger, more powerful canister (where practical). That means picking the 206. The extra filter media space is important, you can never have enough biological filter media. The bigger canister ensures that there is enough flow rate to run the extra chiller, flow is reduced when adding those things mentioned above. And if you find flow is too strong in the tank and blows everything around, it is a lot simpler to reduce flow. Whereas, it's near impossible to increase flow from a smaller, underpowered canister.