For the Pirates, a salary dump on two aging vets, an upgrade as SS, and Bay, they won't be able to resign when he's up for Free agency. In return the get an upgrade, OC for Wilson. An upgrade in the catcher position. one good young pitcher on the verge of ace status, one of the top Minor league SP prospects there is, Rivera, a decent outfielder, Kotchman, a good prospect that's been idled by an illness, and a good veteran reliever.
The ANgels get Bay of course, a guy they can afford to sign to a long term deal, and two aged vets to help out, and Wlson isn't much a downgrade from Cabrera. Napoli can be replaced with top prospect Mathis. Giving up two very good pitchers hurt, but for Bay, it's worth it.