While HOB have the benefit of "easier to clean" a canister offers better flexibility in water control. A canister can be metered down on the outlet side, and have different attachments too, like a spray bar or a larger diffuser (i hooked 3 90° tees to my fx5 to spread the flow across my tank). Also a large canister will use similar energy as compared to a single HOB as they are both typically Mag drive impellers. A single canister will also use less plug space, freeing up some for addittional outlets for bubblers for that fry tank (definitely use sponge filters for them). Canisters also expose less moving water to air so you will have better evaporation control. Just some other thoughts