Surprise surprise: if you compare dynamic shoot-first winger's scoring chance stats to sneaky pass-first playmaker's stats, there's a possibility that first one mentioned looks better.
Since Granlund was transferred from center to winger - happened in 15/16 playoffs - he's been on a whole nother level as a hockey player. And since then he's been playing in a shutdown role with 41,02% zone starts at even strength. That's second lowest of all Minnesota forwards. Despite that he has
CF% 49,21
Rel CF% +1,23
GF% 58,25
xGF% 57,82(!).
69 and 67 points seasons.
You could argue who's the better 5vs5 player but Granlund is absolutely better on special teams, both PP and PK (which Gallagher has never played). These things matter also when you compare who's the better player.