I have a Penguin 350 I use to plant Pothos in. Decided to remove the wheels though for a few reasons but probubly the most tangible is that leaves from the plants inside the back reservoir would jam the wheels. I love the fact that on water change day when the water level drops to 1/3 after re-filling it starts up without having to prime its reservoir like my AquaClear HOBs require 16oz. The only thing I don't like about the penguin is that the intake extension is not water tight and will lose prime early. I keep promising myself that Im going to silicone that extension with the funny valve shut and watertight, but Iv never get around to it LOL.
HOB's have a special need for me now strictly as nitrate filters that almost require no filter replacement once the plant roots penetrate the filter pad, keeping nitrates much lower now between my bi-monthly water changes to between 10-20 PPM. My favorite HOB ironically has turned out to be the Aqua-Tech 40-60 becasue of it has a largest reservoir but the narrowest design to fit behined the tank just under 3" and because I can do a 25% water chnage without having to shut it down unlike my penguin.