Not sure where you are located. I'm in Florida. Haven't had Sam's cakes. Wal-Mart cakes are terrible compared to Publix cakes. I would suggest you try their smaller cakes or cupcakes as a tasting before buying.
If you wanted to go a cheap route I'd do publix. They have great cake for it being so cheap! They were at a bridal show I went to and have a few cake "designs" to choose from. They are generic, but look fine and taste good!
I dislike Sam's club bakery anything. However, check with your local grocery stores & ask for a tasting appointment. I ordered the cake for my first marriage from a grocery store. The price was very reasonable, the cake was delicious & they did an awesome job! They delivered too! No matter where you buy a cake, ask to see pictures of their work!