In search of that evidence, we came up with an idea. Throw the two teams' rosters into a pool and have a draft. If there was some kind of disparity in talent, it should show up in the process of picking teams.
All of the details are below, but let's cut to the conclusion: the Rays' talent matches the Phillies through about the first nine roster spots, then obliterates it through the rest of the roster. In the draft, six of the first nine picks were Rays, though you could argue that the ninth pick (Carl Crawford) was a mistake. Even at that, it was even through the first 19 picks: ten Rays, nine Phillies. That's the top of a roster, more or less: a lineup, a starter, a high-leverage reliever.
Fourteen of the next 21 selections were Rays. The entire middle of the draft was Rays. By the time we got through 40 picks, the remaining pool consisted of nine Phillies and Michel Hernandez, who hasn't played yet this postseason. As Jay put it, "Even into the bench and the deeper bullpen, the Rays' players generally wound up getting chosen before their Philly counterparts."
That's the reason to pick the Rays in six, if not sooner. They simply have more talent than the other guys do.