Look, I think that Crawford is the better player, and he's definitely more exciting, but I think that Werth is a better fit for the team. First, Werth is a little older so he probably isn't trying for as many years, and his contract should be for a smaller AAV than Crawford (at least by demands), so with the amount of money I think we're going to have to shell Gonzalez, I think that we'd save money on Werth over Crawford.
Second, I think that Werth is a more balanced player. Crawford is about speed, a little power, good defense (range) and more speed. While nobody will deny that Crawford is a great player, I just think that pure speed isn't something that the Red Sox regularly utilize. In addition, while his range is impeccable, we already have Ellsbury in Center, so having Crawford in one of the corner OF spots (especially LF in Fenway) doesn't properly utilize his speed defensively. In addition, Werth has the ability (speed and arm) to play RF which can move Nancy Drew to left to "hide" him from his lack of speed and potentially lessen his risk of (daily) injury.
Not to mention that Werth is right handed in a division that has Sabathia, Price, and quite possibly Lee. Werth has the power to tee off on the Green Monster, and he has very underrated speed as well. Werth is a more balanced player that can really FILL OUT the stat sheet. He's also a very efficient baserunner. His SB CS numbers when compared with Crawford are
2008: 20/1 vs. 25/7
2009: 20/3 vs. 60/16
2010: 13/3 vs. 47/10
And that's including the fact that Crawford played in the same division as the Red Sox and the Yankees, meaning that he can absolutely run track on Martinez and Posada which helps his SB numbers.
The only thing I'm worried about with Crawford is him going to the Yankees. I think we'd be hurt more with Crawford on the Yankees than Werth, but with the Yankees likely going to sign Lee, then I don't see them signing Crawford as well. I see Crawford being on a team like the Angels where his style of play fits better with the mentality of the team.
For all of those reasons, plus what's already been said in the thread, I think that Werth should be the player the Sox sign, then put in RF and move Nancy Drew to LF.