There's the season, and then the franchise.
I'd say Beckett, just because I think Crawford can contribute more in the future years. I'd force Crawford to get his damn surgery now so that he'd be fully recovered earlier.
I think there are 3 kinds of players we can choose.
1. Players that are completely useless/redundant/suck. ie: Punto and to a lesser extent Melancon. While I agree they suck, losing Punto doesn't save much money or generate many wins. His contract will be up after next season anyway.
2. Players with large contracts. This will help the franchise the most. Crawford would be the biggest example, Gonzalez (not that he'd be chosen) as well as Beckett/Lackey are also good choices.
3. Players that are toxic to the lockerroom. There is some overlap, but Beckett/Lackey suck and are complete *******s. Youkilis would also be in this category.
As a whole, I vote Beckett just because he's the biggest ******* on the team, is owed more money than Lackey, and Lackey has a year at the league minimum and is 500K/year cheaper in the next 2 years. One more of those can afford Nick Punto.