When discussing Tampa, you must consider Stamkos's heavy playoff regression. So far, while he's mostly been a franchise-quality player in the regular season, come the playoffs, he's more of a 2nd-line forward/PP specialist.
Otherwise, obviously Toronto's forward group is stronger, and Tampa's defense is clearly better. Both teams will have cap problems, but Tampa's are probably deeper. I do think an x-factor is Tampa's culture/front office. Culture does matter, and I'm not sure (even with the GM change) if Toronto really has a winning culture. Dubas seems like a sharp guy, but apparently, some of the questionable moves and picks were made under his guidance. It can't help that the market and technology leads to a lot of pressure on the players and affects their play.
Toronto's forward group as it stands right now is...
Matthews, Tavares, Nylander, Marner, Marleau, Kadri, Hyman, Brown, Leivo, Kapanen, Johnsson, Ennis, and probably Lindholm. Compared to the Tampa forward group...
Stamkos, Kucherov, Point, Johnson, Palat, Miller, Killorn, Gourde, Cirelli, Paquette, Callahan, Erne, Conacher, and Andreoff.
Toronto's big four certainly has the edge over Tampa's just because all of them are 1st line talents and Johnson isn't but the difference isn't vast and it's made up for by the depth Tampa has up front that's better than Toronto by a hefty margin. The other thing about it is that Tampa actually has a future with these guys pretty much wrapped up and a blue line. Toronto will either have to go cheap on the blue line and somehow get worse there or they will have to move on from Marner or Nylander to afford one of those two plus Matthews and Tavares.
As for Stamkos' playoff quality, he was one point shy of a point-per-game in this playoff run. I think his playoff woes are exaggerated.