The top 6 forwards/top-2 d/goalies for both these teams are pretty stacked, so I don’t think that will decide the series.
What Boston will want to exploit is that gaping hole on Toronto’s right side blue-line (Zaitsev, Hainsey, insert AHL plug) and tear into that weakspot. For Toronto they will need to be able to exploit mismatches in forward depth (Tavares vs Krejci, the substantial disparity in talent between third lines). Toronto will try to turn this into a track-meet to exploit their relative speed and Boston will try and use their physicallity to punish a softer, skill based Leafs team.