I think Werth would be a better route for the Sox to go over Crawford.
Crawford is 28 and Werth is 31. But Crawford has been playing on turf for nine years and has attempted 460 stolen bases. You have to wonder about how his body will hold up from all that abuse. He also is a fairly low OBP guy (.336) over his career.
Werth is 31 but has better power and a career .363 OPB. He also could command a little less money than Crawford will. He's a right fielder and J.D. Drew is signed through the end of 2011, but has played 201 games in left in his career.
Assuming the Sox retain Jacoby Ellsbury, I'd take Werth. It's hard to see the Sox having an offense with two stolen-base threats playing prominent roles. While the game is changing to a more athletic one, stolen bases remain a weapon that sabermetrically inclined teams will use cautiously because of the risk involved.