Marner's competition and defensive responsibilities went through the roof when he was switched from the Bozak/JVR line to the Kadri/Marleau shutdown line.
The Corsica date ranges are always wonky for me, but it's telling me that over 40games from Jan 1st to April 10th, Marner played 5on5 ToIQoC of 29.47. Aho played 29.32 in that time frame.
In the final 41 games of the year, most of which was on the Kadri line, Marner scored 17 goals. Aho is a good goal scorer in his own right, but so is Marner.
If you're going to try to accurately assess Marner's 2017-2108 season, you simply must recognize how different of a player he was in December on the Bozak line to how he played in March on the Kadri line. 40ish games of piss poor production and scoring against weak competition and then 40ish games of PPG production with great scoring against tough competition. Aho was better for the first half of the year and then Marner was better over the second half. I think that it's completely fair to say that Marner took his game to the next level around the midway point last year (his production exploded mid January) and that Aho has not matched that.