I have had both memberships,as I live where there are no Costco's currently. When we have a Costco (we will in a few months, they're building now), we'll cancel our Sam's membership, (and ask for a refund).
As for the why's... The meats are better, love the sale on the seafood (crab legs for $6.00
), clothes are a good price and selection, holiday shopping for the DP main office and practitioners, Holiday shopping in general, better overall prices, friendliness, always clean, well organized, great selection on all items. Can I say more? I'll have a choice soon and Costco will get my money.
(Look, an answer without politics