Like I said before Nylander >>>>>>>>> Marner.
Marner's a great player, but Nylander showing again that he has that game breaking potential with his speed and skill that Marner hasn't been able to show. He might frustrate people with some uncharacteristic mistakes and sometimes lack of effort/being soft, but damn when you need a clutch goal he's your best bet even more so than Matthews because of his speed.
As much as I like Marner if I had to choose I'd choose to keep Nylander for his potential to make big solo plays like that sweet breakaway goal.