commonsensewithmoney:
The reason I like the Walmart.com deal better is that not only did you get a better credit ($15 vs. $10) but at Walmart.com, you can get free shipping on some items when you ship it to the store or 97 cents on other items when shipped home. At Walgreens.com, you get free shipping when you spend $25 or more only.
Edited to add this important tip by Michelle: Print your confirmation page for a receipt since the email confirmation reduces the price of the gift card.