Those defensive ones don't quite check out. Marner has had a better xGA/60.
Now, it is closer than many think offensively due to tkachuk's play driving, but I'll still give the edge to marner, primarily because of his individual production and better finishing results. (the same reason I don't put Bratt ahead of Marner as an EV offensive weapon)
Defensively, on the PP, and on the PK it is not close.
Tkachuk is one of the best forwards around the net, he creates havoc which leads to plenty of scoring chances for his line. As evidenced below, he's also a pretty good goal scorer, much better than Marner who is a great playmaker but as you can see, the separation is not as huge as it is in goal scoring ability
Goals/60 : Tkachuk 40th with 1.19, Marner 187th with 0.65
ixG/60 :
Tkachuk 3rd with 1.38,
Marner 314th with 0.63
Points/60 : Tkachuk 32nd with 2.64, Marner 12th with 2.91
First Assists/60 : Tkachuk 25th with 1.01, Marner 3rd with 1.42
Second Assists/60 : Tkachuk 155th with 0.44, Marner 29th with 0.64
Tkachuk is better at scoring goals and creating high danger chances, Marner produces more points but makes 2.7 AAV more per season.
Note : and I verified again regarding xGA/60, Tkachuk is at 2.90 and Marner at 2.93
Marner is better defensively but really not the level made out to be in the medias. It doesn't take into account how bad the Sens goaltending has been and the quality of the team these 2 players were playing for. Now and going forward, the tune might start to change