To be fair to Duff, he's been the ONLY player we've had in pre-season initiating dangerous, attacking runs and actually beating the man. He can also cross again.
Definitely him over Milner/N'Zogbia.
Perhaps in a 4-3-3 Barton could flourish on the left, but if we do opt for 4-4-2 then he'd definitely be left wing for me on current form. It's not scintillating, but relatively speaking he's playing like Cantona in a Craggy Island All-Priests Over-75 Indoor Football Challenge Match team.