I doubt there is a way to definitively prove who benefits more. One thing that seems clear from this thread is that there are stats that make Marner look great, and there are stats that make him look not so good. There are some people who only acknowledge stats that suit their agenda and to them, everything else is fake news.
For me, the big picture truth is somewhere in the middle. Marner is very good for 86 games, then he drops off a cliff. When you go from a ~100 point player to a ~40 point player, that's a problem. You can look at all kinds of stats in an attempt to prove that those numbers are misleading, talk about defence, penalty killing and whatever else in a desperate attempt to show that it doesn't matter and who knows, repeat these things long enough and maybe some people even start to believe their own nonsense? But occam's razor would tell you that going from 100 to 40 as the games increase in importance is a problem, a big problem.
Every spring when we get eliminated, the Marnerites disappear for a few weeks. Then they start up again and by November the hype is at a fever pitch and we're bombarded by posts about how Marner's god's gift to hockey until spring, then Marner fades, the team loses, they disappear for a few weeks and the cycle starts over again. I've seen this movie too many times, it's like watching Groundhog Day. The last few years have done nothing to make me change my assessment of Marner, for that he needs to show that he can be effective after 86 games. He'll get another chance soon enough but until then, none of this statistical warfare means anything.