I think we're having a problem with the different versions of the ms2 tires. There are P, P extended load, and LT E rated versions. They have different max pressures. The Ps have 44psi max, the P XLs have 50 psi max, and the LT Es have 80 psi max. Think this explains a big chunk of the different pressures.
You've got to be sure you're comparing apples to apples. Little differences in aspect ratios can make difference as well.
This table shows how many different possible tires we could be comparing.