I have a Costco membership because in Ohio I'm close to both Costco & Sam's club. But here in The Villages the closest Costco is a good hour drive (of course, I have all the time in the world so I can drive there to shop once a month if I want to). There is a Sam's Club adjacent to The Villages (next to the ABC Liquor Store ~ lol). My friend has a membership to Sam's so I can go shopping there with her.
I think their meat departments are very close in the quality of products. I don't like the Sam's Club rotisserie chickens because their seasoning is too salty for me. Costco's I like better. I purchase good beef and pork at either. Sam's Club was the only place I could find the sliced beef short ribs with the bones on top to make Norm's Korean Bulgogi - Costco only had the boneless beef short ribs and I had to slice them into thin planks once I got them home. But both were fresh and excellent quality short ribs. Both had wonderful rib eye steaks - only in multi packs and pricey, but thicker cut and better tasting than what I can find in the grocery store. I also like the way the chicken thighs are packaged.
The big difference, for me, is the Kirkland brand. Sam's doesn't have anything close in quality. And Sam's seems to drop a lot of items more often than Costco does. At least that's my observation. I will continue to have my Costco membership ~ lots of other stuff that is just a better quality and selection than Sam's in my opinion.