Calzaghe UD in a close fight. Think Calzaghe has too much speed and variety for Ward over 12 and he could make it ugly too if needed.
The Hopkins fight proved without a shadow of a doubt that Calzaghe would lose to Ward. Ward beating Kovalev proves without a shadow of a doubt Ward would beat Calzaghe. Speed and volume doesn't beat Elite level boxing skills and A + level ring generalship. It would look similar to Mayweathers victory against Pachow.
Calzaghe gets stifled by a spoiler, who while not possessing the guile of Hopkins, is tougher and mentally unshakeable with a round stealing intelligence unmatched at his weight classes. Calzaghe is tough but Ward is tougher. Calzaghe used volume to beat fighters, against Ward that volume gets severely reduced. Ward is far more versatile and simply a class of fighter Calzaghe has never seen. Ward UD
Clearly feel Calzaghe wins Speed - Calzaghe Combinations - Calzaghe Footwork - Calzaghe Boxing ability - Calzaghe Stamina - Calzaghe Punch power - Calzaghe I really dont think it would be overly competitive unless Calzaghe wanted it to be and fought Wards fight and even then I see Calzaghe as a clear winner