I've been using canister (successfully I might add) since 1989-90 or so.
First canister: Magnum 330
I have either been blessed(fingers crossed, don't want to tempt fate) or alot of the issues people have a related to not paying attention to what they are doing and not having common sense.
When I clean my cans, I take a minimum of an hour, because I always grease the seals(always have), after FIRST cleaning the seals(orings), and the canister and various parts(impeller/motor/media). In addition, I only clean mine every 3-6 months, and my nitrates generally stay at 30-40 with weekly 50% water changes.
I see people say, "oh I can clean my FX6 in 15-20 minutes, it's not hard", and then you see (alot of times/not always) those same people having issues down the road, because they were in a hurry, not paying attention to detail, over tightening lids, seals not cleaned and greased, etc.
I actually enjoy cleaning my canisters most of the time, but then again I have a VERY VERY stressful management/engineering career in IT, and actually therefore enjoy mundane non-technical tasks sometimes. I think of it as something I can CONTROL more or less if I just take my time.
That said, I personally have only had(knock on wood) one actual failure/flaw, and that was a SunSun304B that developed a hairline crack in the lower canister itself, but it merely "seeped" a drop every now and then. I still ordered a replacement lower canister, and put it an a large plastic pail just in case.
To this day, I still have that SunSun304b (and bought 2 more since plus a 302)and wouldn't hesitate to use it again at a moments notice.
Most of the time, it's USER ERROR, but there are surely cases or manufacturer defects just like there are in anything else.
Another way to look at it: How many recall's has your car had? Dam near EVERY car manufacturer has had them at this point if for no other reason than replacing airbags...LOL
As usual with me, YMMV, and I couldn't care less if you don't like cans, or are too lazy to clean them, think they're too heavy, think sumps are better, blah-blah-blah. To me they are actually just simple pressurized, relatively non bypass dependable filtration to me!
Best of luck on WHATEVER you choose....