We wound up getting a car as a last-minute change last year. So I wound up just going to Wal-Mart and getting the stuff myself. However, we'd planned to use a shopping service, so I did all the prep work for it.
The biggest plus for WeGoShop seems to be the flexibility. They'll basically shop at any store you ask them to, which means you can find any of the things you'd find when shopping for yourself. With GardenGrocer, you're limited to the items on their shopping list.
The one thing I did find to be very helpful was the fact that GardenGrocer had an online list to choose from. I found it easier to browse through the GG list and select things than I did trying to come up with a list from scratch for WeGoShop. In the end, though, I wasn't thrilled with the fresh meats, seafood, and deli on the GG site. The selection was limited, and prices seemed very high to me. I also wanted stuff from the liquor store.
So, I decided to use WeGoShop.
I did some cheating to create my shopping list. My local grocery store has a web-order page to have groceries ready when you arrive. I used that to do the shopping and create a list, which I entered into the WeGoShop site's shopping list. (I suppose I could have done the same by taking a notebook to the grocery store and walking the aisles.) What I wasn't able to do, however, was come up with products, sizes, and estimated prices from scratch on my own.