You lost me before the another level remark(lol)! Marner had a couple of good months offensively but still his line bleed goals. Before cristmas he was really bad most nights, he made no one better. Nylander is the one who enters the zone mostly in the AM line, really elite on that important thing in the game, he has a great shot but uses it not enough.
They are very good players when they are on their games, Nylander more consistent though and not dip so low, Marner have a really bad shot(granny warning) and thats something you cant improve so much. Marner are streaky and need open space to excell. In the playoffs the Am line was target hard by the Bruins and that gave Marner time to do his things.
I will say that Marner could be the most overated player on Hf boards, he has made 2 good seasons but in a highscoring Leafs the numbers are nothing special. But he is and will be a great pp player, but in tight playoffs games he will mostly dissapear,