In the past, I have done majority of my online shopping through Amazon, but have become disenchanted with them. Product reviews are bought and paid for by giving their top reviewers the items for free. Their two day and even overnight shipping are a joke, primarily due to their dependence on USPS to get it done.
Walmart has won me over with their two day shipping pass. Not only is it much cheaper than Amazon Prime, but SO much quicker and more reliable. They use Fedex primarily! What a concept! They don't rely on the inefficient, unreliable joke that is USPS. I have had items due in two days come in one day; it is thrilling really!
The only downside as I order more through Walmart.com, is an issue with missing items; today was the second time this occurred. Having said that though, each time I called Walmart over it, they immediately sent the missing item out. Their picking/checking order process definitely needs improvement.