I have had 1 x Eheim Classic, 3 x TetraTecs, 1 x Crystal Profi (JBL), 4 x Fluvals (2x 305 + 2 x 405),2 x Aqua One CF canisters and 2 x AquaManta (MA's own brand externals).
Of all of them... I dont Rate the Fluvals or the Crystal Profi and i binned the two 405s i got for free with a tank. The CrystalProfi might have been good, I think i had a faulty one, the flow rate as awful and it just barely worked (on the larger Osaka tank)...
Fluvals... i compare them to my Fiesta... lots of them around, loads of second hand ones once people realise they are naff and upgrade, cheap to buy... you end up spending a fortune in spare parts before you give up and get another filter... spare impeller, impeller shaft, well cover, pipe tap leavers, pipes, motor, priming shaft... and so on.... not to mention the media...
The Eheim was an absolute pig to maintain... but with a filter aimed at 600L + on a 250L tank with 4 angel fish in, i only had to maintain it once every 6 months, on any other tank, id have got rid of the filter! The turnover was really quite something though, all it had was 5 thick sponges and a bag of carbon/phosex/bionitratex etc...
The TetraTecs were really good, lasted years and years, I did end up with the leaky one eventually but it happens to all filters eventually and in all fairness, i'd dropped and kicked and knocked that filter about mercilessly for a goooood few years! I had an EX700 on a Roma 125 and an EX700 and an EX1200 on my 340L (though was planning to swap the EX700 to another EX1200) they were both good, very good flow rate and huge media capacity because of the shape and design...
The Aqua Manta is probably my favourite now because it is made/designed by the same people who make the Aqua One filters and the TetraTec filters and then have had all the bad points changed...
Got the same good flowrate and media capacity of the Tetratecs, better canister shape like the Aqua Ones, cheaper than the Fluvals bought new, have 4 corner canister clips instead of ne either side meaning no sealing ring is needed (less spare parts cost!), large priming button instead of stick (less spares cost) and a single lever to disconnect the pipes and shut off water (less likely to break asgood design and less spares cost!) and so on... lol