Location (how far are you from the rr?), avalibility ( how quick do you need it?), price in shipping.
*disclaimer* this is just a guess!
quantity of product shipped
door to door transit time
relibility keeping schedule
cost of service
condition of product at destination (damage/spoilage)
knowledge/or lack of knowledge of shipping options
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.