Collie couldn't get open.
Collie is clearly the better athlete and a faster runner. Their hands were comparable. But Collie did not have the innate ability that Drage had to lose his defender and get separation. I saw a multiple games were Collie was blanketed and could not get open. But I have never seen that happen ro Drage.
Collies Game translated to the pros better because he was bigger and faster. But he also benefited from who his quarterback was and his position change to the inside where he was being guarded by nickel guys and third and fourth DBs. And don't get me wrong, I'm not saying he wasn't good. I think he's number three all time. He was great.
Aside from catching a pass the most important aspect of a receiver is to lose your man and get open. Being big and tall and fast and athletic is one thing but less important than getting open, and Drage was the best ever at just getting open.