This is such a difficult question to quantify or answer. I don't think Sid lacking a social media presence really is illustrative of it.
Everything I hear about Mark Schiefele makes me think the guy is extremely dedicated. There's also those kids who moved a continent over at 14 like Provorov to have a better shot.
First hand knowledge wise, the guy I would have to nominate is Tavares. I was in London when he was on the Knights for a brief period of time. I knew some people on the team, and a bunch of them liked to party and live it up (not that I'm knocking this). You would see Kadri, Carlson, Del Zotto, Rinaldo, etc around town. Tavares, despite being the biggest name and known, the guy put everything he had in to being an NHL. While I'd see these guys out at JBR's or Frog wheelin co-eds from UWO and local puck bunnies, Tavares would be at his billets, playing NHL or Call of Duty, going to bed early and rising before everyone else to put in work. His teammates weren't lazy, and they worked, but his work ethic was unmatched, even among a group of guys who became top 6 or top 4 NHLers. I remember the controversy caused by Kadri when he said that he may be as skilled as Tavares, but he never worked like him. People knocked him for either belittling Tavares's skill or being lazy, but anyone familiar with that team knew he meant that Tavares work ethic was unmatched, even by most NHLers. The kid has had a pro mindset since 14.
I'm sure what I said about Tavares, could probably be also said about guys like Sid, Toews and many others. I just happen to know about Tavares's work ethic from his teammates who witnessed it first hand.