When writing an ad copy, lead with the customer’s pain point that your product solves.
Avoid saying that your platform has an A/B testing feature. Instead, make the benefit crystal clear: goodbye guesswork.
Then you can use the extra space on your Landing to properly explain the feature: «Mailchimp takes the guesswork out of creating campaigns people click on. A/B and multivariate testing let you try things out and pick a winner.»