Nike and Adidas are the two biggest names in athletic footwear for a reason — both make genuinely excellent shoes, and both make some genuine misses. Rather than pick an overall "winner" between two brands with completely different strengths, we split the comparison into the four categories where people actually cross-shop them: running, basketball, training, and lifestyle/casual wear. Each pair, from both brands, went through the same wear-testing process: 4+ weeks of real use, a fixed mileage or session benchmark depending on category, and scoring against our standard rubric.
Twenty pairs per brand, evenly split across the four categories, purchased at full retail price with no manufacturer input into which models we picked. What follows is category-by-category, because the honest answer to "Nike or Adidas" depends entirely on what you're about to go do in them.