I don't know what a Rena Smartfilter is, but on my 40g mbuna tank I have a Penguin 200 Biowheel and a Rena Filstar XP3 canister. I really like the XP3. It's not HOB, it's a regular canister. I think mine's about 2-ish feet tall. It has 3 large baskets for media, so it fits tons of floss and biostars for LOTS of bacteria growth. It also has a shut off valve, so you only prime the filter once when you first set it up. It makes cleaning the filter (yes, I do take it apart and clean it biweekly) much faster when you don't have to re-prime it every time.
I certainly don't consider ANY kind of filter and/or media to be a replacement or substitution for water changes or tank maintenance, and I do a 30% change every week. That doesn't make me like the XP3 any less, though. In my experience, it's a fantastic filter, and it was VERY reasonably priced. I much prefer it to any other canister I've ever used.