Yes you should join a faction after you hit Vanguard level 3. Factions benefit from all bounties (Vanguard, Crucible and [u]Eris[/u] edit: Eris bounties do not count) and patrol missions so rank up much faster plus there are additional benefits beside armor and weapons. Crucible commendations won't matter since ranking up your factions gives legendary weapon and armor drops anyway. [b]Faction Shaders[/b] Each faction has a unique set of shaders that can come in a commendation package. These shaders cannot be gotten elsewhere (except the Dead Orbit Revenant shader that you got if you pre-ordered Call of Duty: Advanced Warfare). [b]Faction Ships[/b] The 3 factions each have a unique ship that can drop after level 20 and cannot be purchased and earned any other way. Definitely the ultimate differentiator. Most people playing Destiny don't seem to know about these ships.