One creative per ad set vs stacking several

Building an ad set — solo creative or a stack?

— Single creative: crystal-clear data, you know exactly what's performing, easy to scale the winner. But Meta has nothing to rotate when it fatigues.
— Multi-creative (3-5 in one ad set): Meta picks the best, gives fatigue insurance, but it'll favor one and starve the rest before they get a fair read.

When each:
— Pure testing phase → single creatives in separate ad sets, clean reads.
— Scaling a proven angle → stack 3-5 variations so there's rotation when the lead tires.

Risk: in a stack, Meta often crowns a winner in hours on thin data and never tests the rest. Don't trust early splits.

Test singles, then stack the survivors for the scaling phase.