Have Polaris 9550 sport. Really works well. Can set to clean just bottom, just sides, or both. Can select normal or intense clean. Max clean time (which is what I usually use) is 105 minutes (1:45). I bought the optional "fine" filter, as I live in GA so red clay does get in on occasion - not as much now as grass is doing well. It can only clean until about 1/4 of the way out of the water, so does not clean top two steps or loungers, built in table, or much above existing water line. Does not directly get into rounded corners well, but has a water jet (which helps it climb), which helps move stuff. So I still need to occasionally brush the corners, steps,... before I start it. Also, turn off pump so returns don't blow it over when climbing the walls. When done, you can press "lift" button and direct it to climb up wall by you to remove. Then can easily remove pretty large basket and rinse out.
I have not used any other robotic cleaners, but I would purchase again.