Johnsson has 1 goal 0 assists in 6 games = .17 points/game
Leo has 7 goals and 12 assists in 71 games = .27 points/game
Johnsson has no playoff experience
Leo has 13 games experience
Johnsson's penalty killing expertise in the NHL is unknown at this time.
Leo's penalty killing expertise in the NHL is appreciated and known.
Tampa and Boston are both scoring at more than 22% rate/pp and with the Leafs averaging 7 min/game in the box, that leads to both potential opponents scoring roughly one pp goal/1.5 games.
I'd want to have one of my better penalty killers available to me vs the unknown. I'd want someone who has experienced playoff pressure vs someone who has not, especially in a secondary/specialized role. I'd want someone who can agitate. I'd want someone who can support a Dzone face-off if the primary C gets booted from the circle. I'd want someone who is scoring at a higher rate than someone who is potentially going to score at a higher rate (and yes, I think Johnsson will eventually score at a higher rate than Leo, but he isn't now), and I'll take 'heavy' and savvy over light, young and unproven.
I'll take Leo.