Not sure how you're coming to that conclusion. Again, I'm using the exact same statistics, and those statistics do not say Rantanen is better, except in that one particular game state in specifically this partial season, conveniently right after a long PP drought for the Leafs. Marner has been better at ES and on the PK, and you're ignoring that, just like you're ignoring a more representative sample for these players.
I'm using nhl.com
You can of course see their p/60, g/60, ppp/60, ppg/60.
Rantanen is significantly better this year on ALL of them, other than slightly lower in p/60.
More fun?
Career playoff /60 stats.
[TABLE="class: brtb_item_table"][TBODY][TR][TD][/TD]
[TD]Rantanen[/TD][TD]Marner[/TD][/TR]
[TR][TD]p/60[/TD][TD]2.61[/TD][TD]1.25[/TD][/TR]
[TR][TD]g/60[/TD][TD]0.99[/TD][TD]0.63[/TD][/TR]
[TR][TD]ppp/60[/TD][TD]5.03[/TD][TD]7.97[/TD][/TR]
[TR][TD]ppg/60[/TD][TD]1.55[/TD][TD]0 (lol)[/TD][/TR][/TBODY][/TABLE]
Rantanen is SIGNIFICANTLY better in all but ppp/60. And Marner doesn't have a single playoff power-play goal. And it's FAR more embarrassing if you look at just the past 2 years of playoffs (post elc).
I'm sorry... but other than Marner being better out of the gate as a teenager, Rantanen has simply developed into currently being a better player. Especially when it matters most. And it's not even really close.