The concensus of opinion is that Costco does score higher on customer service and Sam's is a little cheaper.
What I learned that I didn't know before is that Costco is placed closer to more wealthy Suburbs than Sams and they do carry more high end goods.
Here is a pretty good article about both;
Sam's Club vs. Costco Comparison | Cheapism
I am still happy. I tend to be happy. I like Sam's Nathan's Hot dog for a quick lunch when I am shopping and their Angus ground beef is excellent. I bought the things at Costco that I wanted last time I was there and they were bigger THINGS rather than day to day food.
I don't care what either pay their entry level employees. I believe that if you work hard enough you can climb any corporate ladder if you have common sense and the work ethic and don't abuse substances.