I run, amongst others, 7 old 303 Fluvals and they have been very good and still are, although spares are getting short. I also have a selection of Eheims, my favourites being the 2229 wet & dry, got 3 of these. I also have a Eheim bucket filter which is brilliant, and 3 FX5's. I have had newer Fluvals but I don't think they are as good as the old ones. I also have an old 403 which is bullet proof. All the time of using the old Fluvals I have never had to change an impeller, but plenty of stems, sealing rubbers and clips and suchlike.
I will always favour Eheim because of the availability of spares, as previously stated, Fluval change the models too much.