Not that I'm an expert or anything but I'm leaning toward the .22.  Light, small, ammo is light and small.  Whatever survival situation I'm in I'm going to avoid a gun fight with someone else so people stopping power is last on the priority list, I'm going to play chicken and hide.  .22 I would feel more confortable firing in the air (sure it will still travel a long way) as a signal to search and rescue, or kill small game to survive on without blowing them to bits.