For Rep? Bounties without a doubt. Theoretically you can go with a Faction at 20 so all your bounty rep gains go towards one goal versus having them split between Vanguard and Crucible. Assuming that you can PvP.
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1) Do the Nightfall (if possible) for XP buff. 2) do the weekly strike 3) do daily bounties for the rest of the week with XP buff.