Despite the fact that every non-New Yorker across the globe, including several indigenous New Guinean tribes who have not yet been touched by civilization, are sick to death of the Yankees winning all the time, you have to give them the status of World Series favorites. But really, there are only two bases for substantive postseason predictions.
Talent is what wins, coupled with luck, and that's all there is.
This is the single most important difference between the regular season and the postseason, and must always be at the center of any postseason analysis. Throughout the season the Yankees had some great front-line talent and some terrible guys filling the gaps and giving the good ones a chance to rest. But in the postseason, it's a different story. An imbalanced pitching staff like the Yankees', which causes grief and losses during the season, becomes a world-beater. A balanced staff, like the Athletics' or Mariners', becomes only slightly better by cutting out the chaff, because there isn't as much chaff.