All canisters use O-rings, I guess, to create a good seal. Eheims have been known to be very good filters, solild, strong motors. I believe their Eheim classic canister filters are the first ones made, and are STILL being made.
I own an Eheim Pro II 2128, 2 Eheim Ecco 2234, an Eheim Ecco 2236, and a FilStar XP3, along with Aquaclear 20, 2 Marineland Emperor 280s and an Marineland Emperor 400, The Emperor 400 was my first filter, which was after I had used UGF filters. I had heard so much about Eheim filters, so I decided to buy one. With it being my first canister filter, I had nothing to compare it to, so I couldn't really say I was impressed.
I later purchased a FilStar XP3, becuase I heard it was 2nd to the Eheim, but not the best quality compared to Eheim. The casing on the Eheim Pro II appeared to be sturdier than the FilStar. When the FilStar media pads got clogged, the flow would tend to slow down, which is very noticeable. The Eheim canister filter does not appear to slow down, so I would have to occassionally check to see if I need to replace the media pads. Also the Eheim Pro II 2128 appears to hold more media compared to the Filstar XP3. Both filters are supposed to be for aquariums up to 150 gallons. I had some extra media that I used on my Eheim Pro II 2128. Strangely, the extra media was enough to fill ALL the media trays in my FilStar XP3, which I knew would not be enough to completely fill the Eheim Pro II 2128.
I have heard that people have had problems with FilStar filter O-rings require replacement soon and also lubricating the connections, but I haven't had to do that with mine yet. Though I have the replacements parts already.
I recently purchased Eheim Ecco filters, becuase I needed smaller filters for smaller tanks. I actually like the Eheim Ecco filters, becuase they are allot simpler to use. Even much simpler than the Eheim Pros. The handle makes it easy to stop/prime the filter and also carry the filter from the tank to the sink for easy cleaning.