To me, the Norris should go to the best all-around defenseman in the league, not just the guy who scores the most points. That means the winner should put up points, but also be a solid presence in his own end and the guy who the coach turns to when Crosby's on the ice or the team is down a man.
If you look at stats other than simple points (which Subban leads with a point a game, versus Suter's 0.76 PPG), you get a better picture of the relative contributions of each player. Subban is the more physically punishing, with 43 hits to Suter's 28. But Suter blocks more shots (55) than Subban (41). Subban has twice as many giveaways than Suter (32-16). He slightly beats Suter on takeaways (8-6). Subban is a much more potent weapon on the PP, with 21 points to Suter's 13, playing comparable minutes per game. (That said, because of his extra games played, Suter actually has 16 extra minutes of PP time on the year.)
The even-strength ice time is an issue, as mentioned by others. Suter plays 20:50 minutes 5-on-5 a night, while Subban gets only 17:09. 93 other defencemen in the league play more at even strength, including other Ds on Subban's own team. That could imply Therrien doesn't trust Subban as much as he does Gorges and Markov for those looking for an excuse to disqualify Subban. They may not look at the fact that Therrien plays all of his top four defencemen around 17-18 minutes at even strength, to balance the workload. More damaging to Subban's case might be his ice time on the PK. Suter plays 2:26 shorthanded each game. Subban plays a full minute less than that. Gorges, Emelin and Diaz play more on the PK than PK does.
So, all things considered, Subban is an excellent point producer and the Habs would be in big trouble without him. He doesn't really dominate any defensive category, though, if you look at pure numbers. Then again, the Norris voters usually only look at points, so he'll get quite a few checks beside his name.
