Thats a HUGE downgrade in goalies. Price is great this year. Sure Pronger is a great defensemen but I think Prices contribution to the team will be much greater then just one defensemen. It also depends on your scoring categories. If your league is big on goalie stats then it isnt worth it.
Besides Edler is good for a good 40-50 points which isnt that much different then Pronger. If you need PIM you can most likely find someone easily in FA