The ProS2 is the flagship of the range of S2 desks and is built on Ti-Motion© drives and controls from Taiwan. It has enhanced diagnostics in the control box so if anything were ever to go wrong it is much easier for us to identify the problem. It also has upgraded gearing in the motors and the components are all to higher tolerances.
With the Pro S2 can use the Bluetooth function on the handset to connect to a Standing App for your iPhone or Android phone allowing the option to control your desk height, memory function, customised sit/stand cycle, tracking/calculating calories burned and safety support-error alarm notices. There are twin USB ports on the handset.
The Advance S2 differs significantly from the Pro S2 but only in terms of the drives and controls. The metal work is almost identical however the gearing is domestic Chinese as are all the electronics and handset. The motors come from Bosch Germany but rather than a full metal gearing system there are some plastic gears within.
In terms of basic functionality of up/down, noise and anti-collision there is very little to choose between the desks. In terms of durability and stability the ProS2 wins out on both measures but only by a small margin.
For a full analysis see this page https://www.gostand.ie/pages/desk-comparison-v3