Some functionality that keeps me using the Steam Controller has been touchpads for movement, quick gadget swapping with touchpads, quick 180s/gyro activation with touchpads.
I use it to play games like Doom Eternal, Left 4 Dead 2, Spin Rhythm XD, The Finals, etc.
Sadly I don’t find myself doing the same on the Steam Deck opting for the joysticks instead, since I don’t find the placement, smaller size, square versus circle, and flat surface versus concave offering the type of consistency that I use the touchpads for on the Steam Controller. It feels more a touchpad appropriate for slow paced games or just desktop navigation than optimal for the way I use the touchpads on the Steam Controller. And I don’t see Valve delivering on the touchpad end that I would like with the next Steam Controller with all the inputs it would be fitting in.
I use the Steam Controller still for games like Doom Eternal, Left 4 Dead 2, Spin Rhythm XD, The Finals, etc.
Basically any first or third person game that has aiming improvement, but I am not sold on the Deck touchpads as primary inputs. Tried it and didn’t like it. Found them uncomfortable, size too small, and shape resulting in inconsistent swipes as someone who likes to target a consistent 180 on an edge to edge swipe.
So it will be a good controller for dual joystick users who occasionally want to use the touchpads, but not a good follow up to Steam Controller users who wanted a new controller to use the touchpads for a majority of their games.