I was a Sam's member for years. Now I am a COSTCO member.
Meats and other products are about the same, IMO, as well as prices.
However, COSTCO employees are definitely happier in their jobs, from my observations. The founder of COSTCO catches a lot of flack on Wall Street for treating his store-level employees too well in pay and benefits. Wall Street prefers Sam's, for sure.
IMO, the employees at COSTCO are more friendly and helpful than the employees I dealt with at Sam's. They actually seem to like their jobs better.