I would say a lot depends on your personal attitude towards cleaning, also it would be helpful to know what type of pool you have, as well as what sort of debris you have to deal with. For example people that get acorns and other small berry like objects in their pools may have issues with them getting stuck in the tracks and gears of some models, while people with large submerged leaves may find they have clogging problems, while other models may cope better with steep walls or standing ledges in the deep end, etc. Personally I spent many years using suction side cleaners, before buying a cheap lightly used Dolphin Dynamic off ebay in the off season a couple of years ago for about $300. Overall it has been a great purchase if for no other reason than to get a feel for robot cleaners, and their good and bad points, however I can say my next robot will be one with a remote control to so I can steer it back over spots that it may miss on its random pattern routine.
Ike