A/B tests and Multi-Armed Bandits (MABs) are two distinct methodologies used in data-driven optimization, each serving different purposes. A/B tests involve a multi-step process where a hypothesis is formulated and validated through experimentation, making them ideal for precise measurement and long-term insights. They excel in providing accurate, transparent results and are immune to biases such as Simpson’s Paradox. In contrast, MABs are suitable for scenarios with ephemeral effects, where time is limited, such as short-term sales promotions or rapidly changing regulatory environments. They allow for quick optimization by reallocating traffic to leading variations, even though this may result in skewed estimates due to shifting traffic allocations. While A/B tests are considered the gold standard for accurate measurement, MABs offer a pragmatic solution when speed is critical, highlighting their value in specific contexts where rapid adaptation is required.