A/B testing is a traditional technique in direct marketing, and it’s common in digital marketing, too. People test alternate versions of landing pages, images, email subject lines, colors, offers, creative, and on and on. (In some cases when they have large volumes they may do multi-variate testing, too.)
But don’t necessarily assume that just because one option won that it’s always better.
Liberty Mutual tested online ads with “auto insurance” versus “car insurance”. One got more clicks, but fortunately for Liberty Mutual they looked deeper. What they found was that the people who clicked on “auto insurance” were a different demographic than those who clicked on “car insurance”, and the two groups reacted differently to offers.
So don’t always accept the surface results of your testing. There may be more going on than meets the eye.