The alcohol Garden Grocer provides now is only whats available on their site right? I know they used to be able to go to a package store and get what you wanted.
I think this points out the difference in the two business models quite well.
Garden Grocer has what they have on their shopping list, which is marked up slightly from what you'd pay in the store yourself. I haven't heard anyone complaining about lack of selection, so I assume their shopping list is adequate for most folks.
WeGoShop will shop anywhere you want (including Costco, Super
Walmart, etc) and buy any brand, flavor, size you specify. They bring you the receipt from the store, and add a small service charge to the total. There is no markup on individual items.
With either one, you can have groceries delivered to your resort without you there. The resorts have refrigerators for that purpose, so you don't have to be present.
With either one, you are obviously going to pay a premium for them shopping and delivering, but it's a small amount for a huge convenience -- especially if you are flying in and won't have a rental car.
In the distant past, service complaints have been reported here on the DIS with both companies -- but those were several years ago and I haven't heard any complaints about either one in the last 2-3 years. I think you'd be fine with either company.