I will start by adding the leafs.
Right now we have to be the better team. The experience Reinhart and Eichel got from last year (think how they looked second half vs first) will be huge. Matthews and Marner will be good but it will take time. Long term, as the teams are currently constructed, I like Buffalo more then Toronto. My fear is come free agency they may be more likely to sign some big names. Sure Stamkos didn't sign there but Tavares is lurking and I think when they start winning some games, there will be some good players who want to make that jump over. Still, FA is not how one builds a core team. Either way it should be one hell of a rivalry for the next decade plus. Expect some playoff series to go through each other in the not too distant future....