I tried gamepad and its a joke as far as I'm concerned.
Even switching the assist features off, it doesn't feel right. There's a turn speed limitation of some sort if you make right stick inflexion quickly from centre to furthest away. I then used the Steam Controller's mouse-joystick where its easier to test that motion (which emulates mouse movement from the stick, usually flawlessly) and that had the same issue.
The game does not support simultaneous mouse and gamepad, which would the ideal solution for me with these third person shooters - so I can't use the Steam Controller in that way.
The only option that feels fine, is keyboard and mouse (or the same with the Steam Controller). Less finesse in movement without analogue stick movement, but the KB and Mouse controls compensate well enough for this, so it isn't an impediment. Strongly recommend KB+M