As Hopkins aged, he became VERY defensive as MANY older fighters do, but in his prime circa 1995 to 2000, Hopkins was far more aggressive coming forward with VERY impressive offensive work. Look for some of Hopkins' old fights circa 1995-2000 like the Lipsey fight, and the great battles with Antwun Echols. Hopkins fought like Trinidad at times in that era.
Hopkins could box, he could slug, he could counter-punch, fight coming ahead or going back, he didn't resort to as much dirty tactics then either. Multi-dimensional fighter then as well as now, but he's lost much of his speed now.
I've long been a fan of both Hopkins and Calzaghe, and the Hopkins/Calzaghe fight should have been made in 1999 or 2000 when both guys were at their best. Hopkins won the middleweight title in 1995; Calzaghe won the super-middleweight title in 1997.
Calzaghe's now-brittle hands were still pretty good, and he knocked people out then, no "Cal-Slappy" then. Joe was more aggressive then too, not a light-handed boxing volume-puncher like he is now. Many reasons why the fight never happened among then Calzaghe's promoter Warren wouldn't risk it; Hopkins had court battles with boxing suits.
At that time in 1999 or 2000, I'd go with Hopkins all the way; now with Hopkins well past-his-prime and 43 years old to Calzaghe's 36 years, it may be a different story.
It'll still be a good fight, but it's really too bad that they didn't meet in their respective primes 'cause it could've happened when they were both younger with young mens' styles, full of piss-and-vinegar!