I have had a lot of experience with both types and I prefer canisters.
Most HOB's I've seen lately make you use their brand of prepackaged disposable filter pads/floss. It seems redundant to throw away filter media once it's established with good bio-bugs simply because they make the filter pads impossible to rinse. They clog too quickly for my tastes, plus they are expensive to constantly replace. There are a few HOB's that are good quality though, at least that I've dealt with. Aquaclears and HOT Magnums w/ the Bio-wheel are nice filters that hold a good amount of filter media that can easily be rinsed if need be. The aquaclear also has a flow adjuster, so the current can be controlled and slowed. Both filters are almost like mini-canisters that hang on the tank.
Canisters tend to hold more media and are often customizable as far as media type(floss, foam, ceramic rings, etc...). And due to their larger size, the don't require cleaning as often. Some are a pain to clean, hard to prime, and can take up more space often because they are designed for larger tanks.
I guess it all comes down to situation and preference. Smaller aquariums would work best with HOB's and the same can be said for larger tanks and canisters, but everyone is different
Personally, I use ZooMed Turtle canister filters(small with a spray bar) as well as sponge filters on my 40 gallon.
