Although this is two years old, this is an interesting conversation. I have experience with HOB, canister, and wet/dry . The HOB don't do a good job with collecting the debris, seeing as the intakes never reach the bottom(usually half way down). I'd assume they would be more efficient if the height of your tank was less than 18".On the other hand, canisters usually have longer intakes, which help collect the remaining debris that the HOB leaves behind.I use both(canister and wet/dry) in my display tank because they both serve different purposes. My sump is strictly used for beneficial bacteria and skimming the water. I also use its output to keep the flow direction towards the intake of the canister.
My canister takes in all the debris that sits on top of the sand. As far as maintenance and the sump,Rallyman nailed it. All that needs to be done is changing the prefilter or rinsing it off.Canisters require some time and needs to be turned off prior to cleaning it. How often a canister needs to be cleaned depends on the number/type of fish in the tank. I can't go 8-10 months without cleaning the canister because i have messy plecos that shred zucchini/cucumbers into pieces that get sucked up by the intake, which reduces the output of the canister.if i notice the output slower than usual, than i know the canister needs to be thoroughly rinsed, or possibly new media. Various factors determine how often a canister needs to be cleaned. Also, keep in mind a sump takes up lots of room whereas a canister may take a fourth of that. This is the problem i have with my stand. The sump takes the whole lower bottom, which forces me to have the canister sit on the outside of the stand.