I'm talking a little more long term, looking at the last 5 years. In that time Tampa have 2 Presidents' Trophies, have finished 2nd in their division twice, and reached the ECFs twice. Boston's got 1 Presidents' Trophy, two 2nds and a 3rd in division, and has made the SCFs once and the 2nd round once. The one time in that period the two teams clashed, the Bruins of course lost in 5, and our regular season record against them is not favorable. So purely in terms of results the two are pretty close, and while Boston's gone closer to a Cup on one occasion, Tampa's been a little more consistent.
On top of that Tampa's roster has been stronger and deeper in that period, and is widely regarded as having been the best in the league in the last couple of years. That they've wasted it thus far, and that Boston has done as much if not more with less, is a credit to the Bs, but I still see Tampa as the current benchmark for the east, with the Bruins just behind. If we want to change that order, then we need to beat them in a playoff series. No time like the present - I'm not afraid of Boston facing them. I want to see it. That way the question of best in the east can be settled one-on-one on the ice.
If they're so strong and deep, they shouldn't have got bounced from the playoffs last season. The "best" teams find a way to win playoff series. Five years ago doesn't matter. Best means best now. They crapped the bed in the last playoffs and they finished 8 points behind the Bruins this season. That doesn't make them the best team in the east. One of the best, but not the best.