It depends what you're doing!!!!!!
Are you continuing on with another pitch? If yes, just use the rope.
Are you setting up to rap, or lower ? If yes, why waste the time to backup with the rope if you have to untie from it anyway. Just use 2 quick draws. Also, I've used 1 sling with 1 biner (not always even a locker) plenty when rapping a bunch of times ::. Depends on the situation!!!!!!!!1