Don't forget the fact that Karlsson had Spezza on his team.
Montreal doesn't have any players that come close to Spezza.
In fact this year, PK is doing while most of their "star" forwards aren't playing to their normal levels.
Spezza's the only guy they have though. I'd rather have Montreal's forwards than Ottawa's.
Also 5 points more than Suter with 6 games less played and 7 more goals which is a pretty big discrepancy IMO.
Suter has more TOI by 4 minutes a game which is pretty big but Subban is more dynamic and deserving of the Norris.
Also Subban brings something Suter never can. The NHL is trying to rebuild it's image after another lockout and Subban is one of the most marketable players in the league, and giving him the Norris (which he deserves anyway) is a win-win for the league.