I've tried both filters... as of right now, I have 2 Fluval 404s running, and my Ecco is in the basement collecting dust.
Don't get me wrong, I love my Eheim 2026, but the Ecco IMHO is a waste of plastic. During the entire lifespan of that filter, it was constantly noisy... and I did everything to try to fix it. While preforming a routine filter cleaning, a piece of the filter snapped off when I proceeded to close the filter. Of course, since the filter wouldn't properly seal anymore, it was useless. I should have spent that money on a fluval or a rena (of course, hindsight is always 20/20). Eheim filters are great, but their Ecco line is not even worth a look.
The one fluval I have on my 66 gallon has been in continuous use for about 2.5 years, the one on my 70 gallon has been in use for about 1.5 years.
Try looking into the Rena Filstar xP canister line... I believe they are only a few more dollars more expensive than the Fluvals, but from what I hear, they are solidly built, and work quite well.
HTH
-Richer