GardenGrocer and WeGoShop are two entirely different concepts. You need to think about which one suits your needs better.
GardenGrocer has a set shopping list (a very extensive one). You pick the items you want off their list. They charge a $12 delivery fee, which is free if you order more than $200 of groceries.
WeGoShop is a shopping service. They'll go to whichever store you specify and search for whatever items you indicate. They don't have a set list of things to choose from. They charge a fee based on the number of stores you send them to and the total amount you spend. The more you spend, the higher their fee. Fees start at $17.
One big advantage of WeGoShop is that you can send them to the Super Wal-Mart and get groceries as well as any other items you might need but not want to pack. Ice chest, beach towels, other things Wal-Mart sells that grocery stores don't.
Buying directly from Disney is expensive and their list isn't as extensive as the other services. However, the big advantage is that you don't need to be there for the delivery. They'll put your groceries in your villa, and even put the cold stuff in the fridge for you.