No you couldn't, suppose your A does better in the first market and your B worse (accounting for size) in the second. You choose A. Which does even worse in second market. B was doing the best job for the second market, it is just that market is less open to your product, B would have totally pwned in the first market.
You have to do the A/B within the same market to get useful results.
You have to do the A/B within the same market to get useful results.