With this tool you can determine which is the best ad from a A/B split test. Just let your campaign run a for while and plug in the numbers to see if the difference is significant.
Calculator comes here.
How to interpret “confidence“:
0-90%: No meaning, continue testing
90-95%: Getting closer but still unsure, continue testing
95-97.5%: You are quite sure
97.5-100%: You are very sure