Keita seems much more all action and willing to go forward than Jorginho, although I haven't seen either player that much. But Jorginho basically stays in position, and controls the game with his passing, something we don't have in the side either. Henderson is, when fit, a good defensive number 6 in my opinion, if not perfect in that role.
A peak Lucas would be great though, as I think his passing from deep was underrated. He was quick and clever on the ball, as well as being excellent defensively. If the defensive midfielder is a good as him on the ball, I wont complain. Not sure Ndidi is, but again, I haven't watched him closely.