Neither....
First, go get your rig weighed while it is loaded and ready for a trip. Get weights for all four corners (if possible) or at least front and rear.
Second, go to the Michelin tire weight inflation chart
HERE and download the PDF file.
Third, match up your actual weights and the size of your tires and find the correct inflation pressure.
Forth, Inflate the tires to the recommend pressure while the tires are cold. Any pressure increased during driving is taken into consideration with the chart.
Hope this helps
Ron