I'd play Bellerin tbh.. the more I see of Chambers, the more I see him fit for CB over a winger. Bellerin might fuck up but at least he has pace to get back and may be save his bacon. Chambers on the other hand looks like a bag of nerves!
Bellerin all the way. Better attacker, recovery pace, brilliant crosser and he knows how to head the ball. Chambers is a DM not a defender.