The new "Creative Testing" feature at the ad level is essentially a more user-friendly way to set up a split test. It’s designed to help less experienced advertisers, or those running very simple tests, structure their campaigns.
What it actually does:
It creates a structured A/B test. Instead of you manually duplicating ad sets, this feature automates the process. It's often just a different UI for what you're already doing with the A/B testing tool at the ad set level.
It ensures a balanced spend. When you use a proper A/B test, Meta's system is designed to evenly split your audience and budget between the variations. This is the one major difference from just putting all ads in a single ad set—it forces the algorithm to give each creative a fair shot at the beginning.
The catch: While it aims for an even split, it’s not perfect. It's designed to compare the ads for a predetermined time or until it finds a statistically significant winner, at which point it may begin to favor the winning creative.