At least this last season it’s Gaudreau.
Panarin has had better years than this last season, but the past is past unless you mean “better career”. Until he bounces back and or Gaudreau falls off, it’s Gaudreau
Panarin seemed to have an off year (relative to league scoring increase) when everyone else was scoring more; also he’s had better linemates in the past at times than Gaudreau had if you’re looking at career numbers. This past season is the the best help JG has had in a long time, which I don’t mean as a knock on him.
Gaudreau outscored him (especially 5v5) and had better defense and underlying numbers. Panarin had worse defense and had worse underlying numbers than his own past seasons tho that seems to be team-wide in New York this season.