The 206 is basically the newer version of the 205, they're both rated for up to 40 gallons.
I don't know how much you are going to pay for it, but if it is in the 80-90 range I would get a 305 on amazon for 89.95 ($3 more expensive than the 205) and you get a 3-year warranty.
I have a 306 and I really like it, other filter in that price range that I would consider is the aquatop AKA sun sun I also have a CF
and it is pretty good (I've heard that it is similar to the eheim) the only thing I don't like about the aquatop is the material they use for the canister I think that it is not as resistant as the material fluval uses, but besides that it works pretty good too plus it has the UV
bulb and a surface skimmer.