Maybe I'm just a victim of the aforementioned "need to watch the games" bias, but I've never thought of Kopitar as superior defensively. The advanced stats point towards him being pretty good, though. 5v5 at 6% Relative Corsi and 6.2% Relative Fenwick put him in the top 20 and by straight CF% and FF% he is second in the league behind Bergeron. Plays lots of shorthanded time as a percentage of his team's total; not as much as Bergeron, though more than Toews.
Perhaps advanced stats are where the nomination came from?
At any rate, I think Bergy gets and should get his second. The guy put up the best 5v5 CF% rel and CF% in the league with a 5 v 5 O/DSt% of ~46%. Only one other guy in the top ten in CF% rel was below 50% O/DSt% and no one in the top ten in CF% was, though Joe Thornton, at 11, was at ~47%.