Who said he was the best D man to ever play the game? For his era he was top 3, Lidstrom would have to be ahead of him, debatable between him and Niedermayer. But neither of those guys brought the nasty, physical edge Pronger brought. That edge is something that never gets factored into Norris voting, but definitely plays a part in the game. There's a reason ultra talented guys like Robert Nilsson don't last in this league, and it's because they are unwilling to pay the price to go to the front of the net. Pronger charged a higher price than most.
Nobody is saying it's an easy choice, you really couldn't go wrong with either, but on this team I don't get how the answer can be anything but Pronger. A defensive rock who can take every 2nd shift, penalty kill, play the point on the PP, and put up 50+ pts and 100PIMs (nearly all of the intimidating variety)? I'll take that guy.