If you are driving it on pavement much, I would spring for the ARB's. Spooled or welded diff's put a lot of stress on axles when turning on pavement, and lockers require a real change in driving technique to make tight turns on pavement (I would rather use a spool).
ARB's lock on demand and are open diff for most of the time, but do require 70-105 psi air to the diff's to operate. And ARB is the only one to put up front if driving on rock or pavement, unless you want to keep getting out and unlocking a hub to make a turn. IMHO