Playing at home is a bit like having the serve in tennis: It confers a distinct advantage. As between two evenly matched contestants, the one with the home field/serve will win most of the time.
The Yankees "held serve" for two games at home, and then "broke the serve" of the Angels in the middle of three games played in Anaheim. It is this fact, and not the 3-2 tally, that suggests that the Yankees are the better team.
(If Los Angeles was leading 3-2 by virtue of their homestand, it would be far less clear they were the better team.)
Now that the playoffs are back to Yankee Stadium, the Angels have a very steep hill to climb. Asking them to "break serve" even once on the Yankees' home turf is asking a lot. For them to do it twice would require a miracle.
Nevertheless, the Yankees need to win it in six in order to be more than a slight favorite against Philadelphia. That's because their other weapon is C.C. Sabathia.
He's the one whom they wouldn't want to use in a Game 7, so he could be available for three games against the Phillies.
The Yankees play the majority of their games at home because they were the top seed in the American League. The Yankees would have this advantage against Philadelphia as well, by virtue of the American League's victory in the All Star game.
Sabathia did lose eight times in the regular season (only once after July 31st), but only one of those games was at home. If he were to pitch Games One, Four, and Seven of the World Series, he might win at least the two home games, and possibly three times against the Phillies.
Three wins in Sabathia's games would force the Phillies to sweep the remaining four to win the World Series; two wins would force the Phillies to win three of the remaining four.
Which brings us to tonight's other topic: Andy Pettite. If the Yankees win his game tonight (whether or not he gets the decision), both he and A.J. Burnett would have contributed a game apiece in the ALCS, meaning that Sabathia put them over the top. Then one could hope for the same against the Phillies.
If Pettite loses tonight, that paradigm will go out the window. Then two wins by Sabathia might not be enough—meaning that the Phillies might actually have a chance to win the World Series if they can defeat Sabathia in Citizen's Park.
The worst scenario would be a loss tonight (or tomorrow), followed by a seventh game Monday, because of a weather postponement. Then Sabathia would not be ready even for Game Two of the World Series.
The result is that he'd have only one road start and one home start (instead of two home starts in Games Two and Six). It's possible that even Sabathia might not be deliver two wins under these circumstances. And even if he does, one would have to worry that Andy Pettite will not deliver even one win.
None of the worst scenarios apply if the Yankees win Game Six and there is no Game Seven...which is why Game Six is so important.