I'm sorry but you are the first person I have ever heard say that a canister is better than a sump so...I'm going to go out on the limb and have to disagree with you. I've had canisters, HOB's and a sump. The sump is by far the easiest to maintain and is definitely the most effective. As I mentioned before, canisters have their place, but for big tanks with expensive fish, I don't think anything will perform better than a sump.
Also, as far as the reliability of a sump, if set up properly, they can be very reliable.
A sump is definitely harder to set up at first. However, it creates a much easier maintenance and a better system.
As far as oxygenation, sumps are much better at that too. So, according to your comments about bio filtration being only as efficient as the oxygen level allows, a sump is better at that too.
I think that the only thing that might be better thank a sump is the ultima filters (which are basically large canisters, I know) if the tanks are too big to make a sump very achievable.
I still say, sump all the way!