Yeah... those recoil calculators may be scientifically accurate, but they certainly don't always tell the whole story. The slow shove recoil from a 12 gauge, hot 45-70 and 375 type loads are less offensive to me than 300 Win Mag type recoil.
The other thing that can't easily be computed is how the rifle fits you, what type of pad it has and what you might be wearing. Weight also makes a huge difference. I know it goes into the equation, but I think some folks forget about this. I used to have an 10 lb 7mm Rem Mag that didn't feel liked it kicked much more than a 6 lb 243.
As far as comparing the recoil form the 300WSM to the old school 300 Win Mag, I've fired both from synthetic stocked Savages and they seem about the same to me. When deciding which gun to buy, I don't think the difference in recoil is enough to worry even one second over. If you don't like recoil, you ain't gonna like either one. If recoil doesn't bother you, then you aren't likely to be able to notice the difference between them.