I consider them about equal man defenders, maybe a slight edge to Al. His size and instincts on centers are pretty good. For instance Deandre Jordan tried several post moves on Al a few nights ago and think it was either a turnover or a strip every time. I can't remember any centers ever "going off" on Al. Millsap is a significantly better help defender and in transition.
I never said Al didn't "suck" on defense, don't twist what I said. Just your metric will be wrong as often as it is right. I gave you a clear example of how it could be wrong on nearly every play in the Jazz system and could give many more if you need further convincing.