Haven't seen Gormley play this season, so I can't/won't comment on which of the two is better. But with regards to Gudbranson, I think people are under selling him a bit.
The question going into this season after Gudbranson going 3rd overall was, did Florida pick a player at 3rd overall who hasn't shown much of an offensive game? Folks wondered if the Panthers basically took a stay-at-home blueliner that high. I think this year Gudbranson has answered those questions with an impressive offensive season.
People who have watched Gudbranson a lot (and not just stat-watched) knew he had offensive upside that maybe didn't translate to production the past season, but this year he's putting things together and is producing quite regularly, especially since he returned from the World Juniors. Gudbranson's got 10 goals and 27 points on the season (in only 35 games), and has 7 goals and 16 points in 14 games since the WJC. He's starting to show his potential as a legitimate two-way defenseman, not just a stay at home type.
I believe that anyone who hasn't really followed him closely this season are going to be surprised at how good he's been offensively, as well as his usually solid defensive game and physical play.