I think cost-wise in terms of actual dollars it's really mostly a comparison between the accommodation on-site, where you technically need no other transportation, even to/from the airport, and the accommodation off-site, where you may need the car rental/shuttles etc. Everything else is either hard to quantify (earlier and rolling FP window, rolling dining reservation window, the 'magic' etc) or highly dependent on your family's needs. Someone staying on-site may indeed incur higher dining charges if they ate every meal in park or on Disney property, but that same person might decide to use Uber Eats, or take a taxi out for a meal off-site. Similarly someone staying off-site might decide to eat every meal in park. Those costs are basically a wash between on- and off-site because of all the variables.