This year, Marner's stats look better, but he's been A) healthy, and B) consistent. Matthews has had a couple of multi-game slumps, but is still their #1 guy - make no mistake about it. Marner is a 100% lock to remain a Leaf. The consensus is they'd LIKE to get him under $10M, but likely won't. They'll drop Johnson and/or Kapanen before bailing on Marner.
It's kinda like MacKinnon and Rantanen. Who'd you rather have? Rantanen is looking better on paper, but overall, MacKinnon is the better/more valuable player. Or draw the comparison to Sid/Geno. Pick any #1/#2 player combo. Such is the case for Matthews/Marner. As far as 21 year olds go, Matthews is the more valuable asset. Marner will get paid, don't worry. It's gonna be tight to get all the pieces they need under the cap, but it's doable.
Bet everything you own that Marner gets a deal from the Leafs before July 1, and stays a Leaf. The fear around here is that Marner *is* that type of player that can/would get offers from other teams, despite how much extra the price-tag is in compensation to the Leafs.