Ok, so when you buy cargo it just appears as a large box in your cargo hold.Those are the box missions. You can buy cargo by the tonne (or whatever they call it) and you get pallets stacked up in your ship. They look different too
Makes sense for a game with ship interiors, I guess. As long as you don't have to load and unload yourself.
So the difference there between ED and SC is the existence of interiors.