Why the Yankees will win  1. Mo I. Momentum. They burned rubber
into the postseason, winning 16 of their last 20. And they had
to survive a barrage of close games. All that has given them an
edge, unlike some years when they coasted in with wide margins.
2. Mo II. Mariano Rivera. Great anytime, supernatural in
October. Is better than money in the bank; is money in a high-
yield CD. Throwing harder, with more bite in his cutter than
ever.  3. Age. It's become one of their rallying cries. Win
another for Bernie Williams, Jorge Posada, Gary Sheffield, Tino
Martinez, Mike Mussina and Randy Johnson, veterans who may never
come this way again.  Achilles' Heel  Achilles' arms, really.
Sheffield's arm seems loaded again in right field, but Hideki
Matsui and Williams can be run on -- and the Angels are just the
sort of aggressive band to take advantage. They have ways of
compensating -- Matsui with impeccable anticipation and
mechanics, Williams with cutoff men who run out to shorten his
throws. But that only works to