Calzaghe. Better footwork, better hand speed, and more natural at the weight. He probably wins at 175 too. To be fair, Benavidez at CW looks a lot better than he does at 168 and 175. It shows that being huge for a weight is overrated, and the most important thing is being comfortable at the weight you fight at.
Calzaghe did not have better hand speed than David. David was at least just as fast, more accurate and hit much harder at the weight, plus Joe had mediocre defense. Not hard to work out what happens.
Benavidez was a massive weight bully at 168. A combination of speed, power and mean I'm not sure Joe survives.
Based on the evidence of Benavidez vs Plant alone I'd pick Zags for a UD. DB looks a much better proposition at Cruiser which I think is his best fighting weight
Benavidez KO3. Joe got knocked over by enough guys who can't crack. Benavidez massive skill, power, size advantage.
Benavides can not only match Joes pace but is stronger and in my opinion the overall better combination puncher.