I know all of the numbers are in Nino's favor, but isn't there something to be said about allowing him to help elevate the offensive capabilities of the 3rd line (along with Haula)? As long as Coyle isn't a complete anchor to the 2nd line, and he wasn't last year even though some think otherwise; as long as the 3rd line is getting their minutes, I think "spreading the wealth" could have a tremendous positive impact this year.
Ideally you just want highest net scoring. But I would argue that you want your best players on the ice as much as possible. Unless your 2nd and 3rd lines get equal ice time and relatively similar defensive matchups.
There's an economic cost to moving a skill player down the lineup. We could take it to the extreme to see it easier. If we move Granlund to the 4th line, he would arguably boost 4th line scoring considerably, maybe 10+ goals? But what about that top line? I would argue you would see that line's scoring drop by more than 10 goals, because now you have less talented players getting more ice time and more talented players getting less. Result is a decrease in net scoring.
Another way to look at it is when we look at points per 60 minutes. It's not a surprise the highest scoring players have high points per 60 minutes. If you have a player who has high points per 60 minutes, it's likely that you can move them up the lineup and enjoy that higher scoring productivity.
In other words, points/60 x TOI/game x games played = total points. To boost scoring, get players with better points/60 (like we did in Vanek and Nino) and give the most ice time to the players with the highest points/60.
Two caveats would be small sample size, in which a player had high points/60 due to limited ice time and that would regress to the mean. Another would be an instance of synergy between players that would boost the productivity, and breaking up that chemistry would reduce net scoring. So say you had a player who really did well with Haula, but couldn't figure out how to play with Koivu or Granlund, and scoring goes down.
TL;DR - it's possible Nino is a better scorer on the third line, but I would give the benefit of the doubt to the more productive player and give him more ice time.