Bobby was the better scorer and better player. But Brett was basically only goal scorer. In that sense Brett was better pure scorer since scoring goals was the only thing he could do. Bobby was much more than just scorer.
I still have to vote senior guy on this. Bobby led the league in goals for 7 times!? If he never goes to the WHA maybe even more.
My initial thought was that it was Brett Hull and goal scoring was the only thing he was better at, but I think I actually have to go with Bobby. Both have nearly identical NHL goals per game statistics (0.57 for Bobby, 0.58 for Brett), but Bobby played in a generally lower scoring era (although Brett played it some of the highest scoring and lowest scoring era so that's kinda tricky). Bobby lead the league in scoring 7 of 10 years, and had it not been for his time in the WHA it's entirely possible he could've been #2 all time in goals scored. I think at their peak Brett was still the better goal scorer, but overall I have to go with Bobby.
Brett. It's hard to compare goal totals from different era's. Personally, when I compare the two, I think Brett played in an era with better goaltending and defense. He scored more NHL goals, so I voted for him.