I began Future War Cult because they have the armour buffs I want. Then I realised there wasn't much to choose between that and the similar stuff the Vanguard was selling so I switched back to Vanguard. I don't think Bungie have done enough with the upgrades and visual appearance on gear to encourage people to diversify. There is such a small difference between one piece of legendary gear and the next there seems little reason to grind different rep.