Yup, they all have their role in AH, but from a strat perspective:
The Lancaster carries enough bombs to slam all hangars at a field. It also works great against HQs.
The B17 packs a punch, but is a serious gunship. If you've got a high-profile multiship mission somewhere, this should be your ride of choice. Until they increase target hardness against MGs, the B17 makes a great strafing platform too.
The B26 is just great fun. You can use it to knock down ack, slam Vfields, or blow a hangar; or you can strafe with the guns, and CAP airfields. Nothing is as satisfying as vulching in a b26 (although the relatively small ammo load of the forward guns limits its staying power).
The Ju88 climbs like a dog, but runs fast enough and has enough bombs to deack two fields and close their Vfields.
