So, in addition to the form factor, the difference is that the Dual Switch has 4 buttons for switching 4 different lamps, scenes etc. on and off and a dimming wheel. The buttons can be freely programmed in the Hue universe, so the Dual Switch can be used, for example, to switch 4 individual lamps (groups) on/off separately using the buttons and dim them using the rotary control. The rotary control can also switch on a 5th lamp (group). Dimming and scenes can also be controlled with the buttons.

In short: the dual switch is more versatile to programme.

If you only want to switch one lamp or entire groups in a room, the normal switch is sufficient.

If you want to switch different lamps or groups separately, the dual switch is the better choice.

The switches can also be combined - different switches can control the same groups. I use the Walschwitsch, the normal switch, the Feller and the dual switch. Each has its advantages and disadvantages.