My experience with the EZ Vac was mostly a good one. It would sometimes get stuck behind the pool steps since there was a large gap and I had all the lengths of hose on it, probably should have removed a couple. It sometimes would get clogged by a big leaf or something and I'd have to unclog it. And sometimes it would miss areas as it meandered along clicking along. It has suction ports underneath the rubber skirt, on 2 sides of the rubber skirt and back then (maybe still) their connector to the skimmer was a self regulating valve. I would have to remove the skimmer basket, put the valve into the skimmer throat and it would start clicking along. I never had air leaks but if my pool had lost enough water and we are only talking about 1 inch the valve would suck in air from the vortex it made; so I made sure anytime I used it I had the water up to a certain level on the skimmer plate. Another thing nice about the valve is you are taking water from 2 places, vac head and skimmer so you are taking water from the top and bottom of the pool. Every so often I would manually vacuum the pool with the hoses provided on the EZ Vac and it worked well with that. I never used a leaf canister with it and actually used to watch the leaves flowing by in the hoses but my pump skimmer canister was fairly easy to open and my pool wasn't hard plump so no big deal.
I have no experience yet with my Hayward Cleaner, which is actually the Penguin and not the Aqua bug but I think they are identical except for the outside plastic critter look. If I remember correctly I think the pool store said I can use the cleaner suction lid over the skimmer basket but I'm not too sure on that until I try it. If it does work that way, no need for a leaf canister and it would be much easier to clean than the pump skimmer basket.
Since I was looking up pool stuff today I did see some sort of "vac" that uses either water jets from a hose or whatever to create a vortex into a bag. Concept seems OK except the hose thing could throw your chemistry off every time you use it.