I'd put my money on Boston today, but also think they're more than likely to add another top 9 forward or two by the deadline.
I understand why Leaf fans are excited as there's a lot of talent out there, but I think their team is constructed more to blow away the bottom half of the league playing end-to-end hockey than grind it out in the playoffs against more structured teams. Too many stretch passes and inconsistent forecheck will have them on their heels against teams like Boston, Tampa, Washington, Pittsburgh.