the sponges are only one part of the cannister. there are levels in the filter that you can put eheim pro media in.
you dont have to use all the sponges. when i set these filters up i leave the outer coarse sponges as they are, surrounding the compartments.
then i put some fine filter wool on top of the media (as in on top of it, not in another compartment). there are a lot of media trays, that are pretty darn large. you could easily fit 3kilos of eheim pro media in there.
I use the 2080 for a castle plant tank at the shop here, and given the choice I would have opted for the fx5- but we only use eheims on the shop floor.
you get more for your money with the fx5.
I am one of those that clean cannister filters relatively often, usually once every month or two. but with the fx5 you can make it help with quick water changes, where it cleans the cannister as well.