JMHO... I wouldn't even think twice about it. External canister all the way.
I have 2 Fluval 4plus Internals and a Fluval 304 Canister. I have used them both and the canister is awesome. Now I only use the internals for when I am rearranging the tanks. ( I tend to stir up alot of muck, so I leave one of them in the tank for several hours after the fact to clear out the excess floaties. )
Maybe it's just me but I get water all over the place when I change out the internals. The canister is easy, unplug, disconnect the hoses and take it over to the sink.
The externals have tons of room for filter media, and it all gets tucked away under the tank rather than taking up space inside the tank.
I hope this helps,
"Life is not like a box of chocolates... it's more like a jar of jalapenos. What you do today... might burn your a$$ tomorrow."