So many Halos, so little time. Arbiter chooses one based on how much he enjoyed it. Chief just picks the newest one, assuming that one is the best. Sigh.
Ask Arby n the Chief Tumblr: [link]
Arby n the Chief belongs to Machinima and JonCJG. Halo and all related media belong to Microsoft, Bungie, and 343 Industries. The pic is mine.