We used to be members of Sam's Club, and we decided to try Costco.
The Tempe location is the closest to my home, so that's where we shopped.
Parking is terrible.
Product selection is horrible, unless you like the house brand, Kirkland (we didn't).
Come in one time and find a product you like, and the next visit it's gone.
We tried it for 1 membership period, now we're going back to Sam's.
Sam's has better selection, better prices, and way less hassle.