As someone who works for a major e-commerce site, I am often the one who has the most influence when it comes time to decide which testing method to adopt. Multi-armed Bandit testing can be good, just as standard A/B testing can be good. But the factor which trumps all of these are the total costs of testing (and the return on investment to the business). One must consider the following before undertaking any of these testing methods:

1. Implementation Costs - How much time will it take to implement the testing code? Some tests are easier to implement than others. 2. Maintenance Costs - How much time will it cost to maintain the test for the duration of the testing period? We've ignored this in the past only to realize on occasion that implementation introduces bugs which incur cost and can be disruptive. 3. Opportunity Costs - What is the cost of doing the test versus not doing the test? Consider setup time, analysis, and final implementation.

After going through a few tests now, we have a pretty good sense for what the total cost to the business is. We don't really look at it as adopting one test method over the other, but instead rely upon the projected ROI to test this versus that, versus doing nothing.