Why each team in the NFC East will win the SB or not win the SB

In alphabetical order:

Dallas Cowboys
Why they will win - In the biggest move of the offseason, the Cowboys acquired one of the top receivers in the league in Terrell Owens. Owens is a game breaker and opposite Terry Glenn, this tandum will be very tough to stop. Dallas also has two very good running backs in Julius Jones and Marion Barber and a top notch TE in Jason Witten. The defense is solid with star safety Roy Williams. Mike Vanderjagt has joined the team as one of the best kickers in the NFL.
Why they will not win - T.O. Bill Parcells is already visably annoyed with all of the media attention around Owens. He can break a locker room apart - he did it in Philadelphia. While Owens is solid on the field, he disrupts a team off of the field. Owens was recently fined for missing meetings. That coupled with the fact that the aging Drew Bledsoe is behind center could cause for some tension on the sideline.

New York Giants
Why they will win - Quarterback Eli Manning is coming into his own. And if he is anything like his brother Peyton, watch out. Tiki Barber is one of the best all around backs in the league, they have a top receiver in Plaxico Burress, and one of the top tight ends in Jeremy Shockey. With the offseason acquisision of linebacker Lavar Arrington to go with Michael Strahan and Osi Umenyiora, the defense is solid.
Why they will not win - Manning is still young and makes mistakes. He looked horrible in the playoffs least year. Strahan is getting old and has lost a step. Barber has talked about retiring after this year and one has to wonder if he is wearing down.

Philadelphia Eagles
Why they will win - Coming off a horrible season, the Eagles have a lot to prove after not making the playoffs for the first time in 5 years. Donovan McNabb is the divisions top quarterback. Running back Brian Westbrook can hurt an opposing defense from anywhere on the field. With the addition of receiver Donte Stallworth and the emergence of Reggie Brown, the offense is looking like it is going to put up a lot of points. Both the offense and defense first teamers have looked fantastic in the pre-season.
Why they will not win - The second half of their schedule is brutal, with three straigh division road games, surrounded by games versus Indianapolis and Carolina. Westbrook hurt his foot and misses time every year.

Washington Redskins
Why they will win - Washington has done a lot this offseason. They added receivers Brandon Lloyd, Antwaan Randle El, and running back TJ Duckett. The Redskins already had pro bowlers Santana Moss and Clinton Portis.
Why they will not win - Quarterback Mark Brunell is getting old. Portis is hurt and Washington has looked horrible this pre-season.

There you have it. This will be the best division in football and two teams from the division will make the playoffs. My guess is that it is the Cowboys and Eagles.