Determining the "best" product is not as straightforward as some might think. While some product categories have concrete metrics that can be compared against one another, other products aren't so straightforward. In order to measure qualitative information, they draw on research and conversations with experts to narrow the field of products.
From there, they design a series of quantitative and qualitative tests designed to narrow those products to a "best" one or two. They are completely transparent in the process, and will always explain how and why we came to their conclusion.