That is a tough one. Calzaghe has faster hands but Michalczewski is bigger, has a great jab and very underrated ability. I can see Michalczewski winning a close fight. He sometimes started slow in the first few rounds but came on very strong.
I like Calzaghe by a narrow decision but I say that with no real conviction. Dariusz was the true light heavyweight and theres no telling how good Joe was at that class since we only saw him win decisions over aged versions of Jones and B-Hop, when also being at the end of HIS career. Calzaghe is the better fighter p4p, but I think Michaelczewski is somewhat underrated since he lived in the shadow of Roy Jones.