Sam's only takes Discover, Mastercard, check, cash and debit. Costco only takes AMEX, debit, cash and check.
Other things to consider:
Sam's you can do click and pull or fax and pull. Your cart will be ready for you when you go. Just pay and load your car.
They have a clearance section, but not everything there is on clearance! I have found some wonderful deals like Mr. Clean magic erasers 10 for $1.81. I still think my best deal there though is 5 pounds of Willy Wonka candy for $0.71! They had so many bags. I think my mom now cringes when she sees me calling and I tell her I am at Sam's Club. It means I have found a great deal.
Here is a hint- if the price ends in a "1", it is on clearance. That is their code for get rid of it. So if you see something that you want and see it with a "1", they are dropping the price on it. I have held out and watched it drop week after week. You also run the risk of it not being there though.
Another big plus is gasoline!
If you are not happy with your membership, you can return it for a refund of the difference of the months you did not use.
You can always split the membership with another person since you get two cards. Even though it is called a "spouse" card, it does not need to be a spouse.
If you do get a day pass and see that you want to get somethings (and join), you can purchase a membership and save yourself the 10% upcharge fee.
Since I grew up with Price Club, Costco and Sam's, it is a part of my life. I could not imagine not having a membership. Especially with a baby! My boys love the samples and cookies from the bakery that our bakery gives to kids. Also when we travel, we know that we can get a meal at Sam's or Costco and fill up the van. (We have both memberships)
Good luck!