Amazon Prime Or Costco? Which Is Best?

Costco and Amazon are two of the largest retailers. Both have loyal user bases. Memberships for each company costs about the same. Is one better than the other?
Prices tend to be cheaper at Costco than on Amazon Prime. Costs though are a small part of the equation. If you favor convenience and efficiency over price, Prime will likely come out ahead.
Credit Cards for both offer rewards.Both offer discounts. Convenience is a big difference.