The Other Shipping Options that allow you to charge a label to either the Recipient or a Third Party are helpful whenever you want to use a shipping account other than the one you have integrated into ShipStation.
Ultimately these options result in the same thing - the third party account is charged for the label.
Typically, using the option, Third Party, should meet all of your needs. You may, however, want to specify that the account holder is also the Recipient. Depending on your carrier, the selected option may also display on the shipping label itself or on the invoice for the billed party. If this is necessary for your business, choose the Recipient option instead!
For UPS, FedEx, and DHL Express, you can specify either the recipient's or third party's account information in the Order Details pop-up under the Other Shipping Options panel, as seen in the above screen shot.
This article goes over in detail the steps necessary to charge a third party for a shipping label.