I run a tru trac in my tow rig. Pros- completely mechanical and basically nothing to have fail. It gives a partial rotation of one tire before locking so it's great on the road and doesnt eat tires. Cons- I cant find any.
Air lockers are great but if you get out there and the pump takes a dump, or line gets broken somehow you are open diff. I would go tru trac for your application.
