I personally love UPlay and buy most of my Ubisoft there than through Steam (I love the rewards system - keep giving us good stuff to add)
But I have over 700 Steam games and I also have a Steam controller, so it would be really helpful if you could just link the games to the Steam version (I'm sure you and Valve could come up with a deal)
And please, please start supporting the Steam controller more. I just bought Watch Dogs 2 and getting the Steam controller to work is a nightmare.