Magento 1.7 Models – Difference Between getModel(‘catalog/product’) and getSingleton(‘catalog/product’)

Here's another answer with some information how to import simple/configurable keeping the associations using Magmi. Looks like it should be possible: https://stackoverflow.com/a/16766075/1117286

This is not really Magento related, more of a discussion of terms or semantics. However, to most people the distinction is that in multi-vendor you see that the website offers products actually sold by other parties. With dropshipping, the customer thinks he's buying directly from your store, but actually you're only handling the order on-site and the rest is done in the background by a third party.

To elaborate:

1. In a dropshipping setup, you sell products on your store that are actually handled by third parties. You handle the order-process on your website, after which you forward the order to the third party. They are the ones actually sending the order. In most cases, the client ordering doesn't know about this. The third party sends the package under the name of your website, with your logo, etc.

2. In a multi-vendor setup, customers can choose from several vendors that are selling on your website. Good example are Etsy and eBay, which offers a multitude of tiny shops run by several individuals.

Technically, the most important point is that a dropshopping site is maintained by one person or company. You aggregate products from other vendor(s) and 'sell' these on your site. For a multi-vendor site you need to handle a store for every vendor, provide them with logins to handle their personal store, etc.