Choosing which one I'd want on the pitch out of Bailly, Rojo and Jones would be a tough choice. They're all so deeply flawed. Fitness aside, Rojo doesn't seem to know how to not two-foot someone, Bailly is the worst header of the ball I've ever seen from a centre back despite having an incredble leap, and Jones can sometimes be fairly solid but is stupid and reckless more often than not.
If he could stay fit, then Bailly just about shades it for me, but he's still not good enough. He can be impressive when the ball is in the ground, but he'd probably lose an aerial duel to Juan Mata. It's just too big of a weakness for a CB to have IMO.