I "only" have the S6 Max V, so I can't make a practical comparison from my own experience, but in my opinion the most important difference, apart from the suction power, is the camera in combination with AI, which recognises obstacles and learns. Apparently, the Max V is also faster (but I can't verify that).
In any case, I am completely satisfied with the S6 Max V - we used to have a Roomba years ago, but they are worlds apart.