Well, I guess derailing is OK if moderators are contributing to it.
Mitchell was better than Doughty in which way, precisely?
Doughty faced tougher competition, yet drove the play in a more positive way than Mitchell did. Doughty also started shifts in his own zone more often than Mitchell did. It's close, but Doughty was clearly better last regular season.
In the playoffs, Doughty was easily the best defenseman on the team and in the league.
Advanced stats are great and everything, but they need to be taken with a grain of salt. They provide wonderful depth to hockey analysis, but they also miss nuances that aren't picked up by counting how many shots were attempted, or where someone started a shift and then ended it. Advanced statistics have no way of measuring if a player made the correct read in pinching instead of backing off at the blue line, or if he played the shot instead of the pass on a 2-on-1, or any number of similar types of scenarios. The final result of the play may end up registering in a player's Corsi (or PDO, or whatever advanced stat you want to throw out there), but what the Corsi doesn't tell you is
how that result was achieved. That's a huge limiting factor when including those in an analysis, and a reason why it's best to use them in tandem with physical observations.
All that being said, it was very obvious to many Kings fans from watching the games last season that Mitchell was the better defenseman in the regular season. Doughty didn't step his play up until the playoffs (where I thought he was a legitimate Conn Smythe candidate). Mitchell makes correct read after correct read, whereas Doughty is more prone to mistakes. I'm not saying Mitchell doesn't make mistakes because he clearly does. Hockey's a game of making the fewest mistakes possible, but it's a given that they're going to happen. From my point of view (and a number of other Kings fans, clearly), Mitchell was consistently better at limiting mistakes. He's an anchor on the penalty kill. Not that Doughty is poor, but Mitchell is a huge reason why the Kings have had one of the best penalty kills in the league the last couple years. It's a small sample size now, but the team is middle-of-the-pack in terms of penalty kill this season without Mitchell (and Greene, admittedly).
Ironically enough, even after my little speech up there, I'm going to use some traditional numbers to try and illustrate my point. I understand that points and +/- aren't perfect, but they do help give some extra context here. For all the offensive upside Doughty has, he put up 36 points to Mitchell's 24 last year. Looking deeper into their production, Doughty put up 20 even strength points to Mitchell's 12, while receiving 1 minute more ice time at even strength per game. That's not a huge gap when you consider Doughty's offensive capabilities. Where Mitchell really blows Doughty out of the water is +/-; Doughty was a -2 last season while Mitchell was a +20. Like I said, I know +/- isn't perfect, but it is useful when comparing teammates. That
is a huge difference.
And just for fun, I'm going to use a couple advanced stats:
Goals for on ice per 60 minutes of even strength play
Mitchell: 2.24
Doughty: 1.96
Goals against on ice per 60 minutes of even strength play
Mitchell: 1.49
Doughty: 1.96