The Roborock S6 is definitely the worse model. It only has a small mop water tank that works without an electronic pump and has no 3D no object detection. I think the S6 units are more expensive because they are older. I wouldn't want to swap my S6 MaxV with any of them. The 3D object recognition and the possibility that the hoover can also recognise objects as such was one of the main reasons why I bought the best model from Roborock a year ago. After buying it, it is recommended to update the firmware immediately, because a lot of potential is wasted in the delivery state. The robot has been significantly optimised within a year.