First, I do not reload the 50cal cartridge. Given the way most reloading manuals provide their data, I would look closely at the data on the two different pages for specific differences, like bolt v semi. For pistol calibers, we do find data that is differentiated due to a short barrel, different twist, etc. If you are looking at load data for the same bullet profile/weight, I expect this is why you are seeing differing data on the two different pages.
When I come across conflicting data, I try to determine why it conflicts. Production chamber, universal receiver, barrel length, bullet profile, etc. Sometimes you cannot differentiate why. If I cannot determine why, I take the average of the two, and then use a charge somewhere between one of the starting charges and that average.
That's what I do with pistol and small caliber rifles. The 50cal is a whole different beast, and I do mean beast. If you screw it up, you can screw your life up pretty bad. I strongly suggest you approach reloading this cartridge with a very conservative attitude. It is always safer to work your way up, even if it takes a very healthy bite out of your wallet every trigger pull. But then again, you already knew that when you ventured into the 50cal arena.