"Nosler rates the max load at 26.0 gr and Speer rates it at 27.5 gr. Thats quite a difference."
They didn't use the same rifle! Even if they had, it wouldn't have been your's!
"I always start low and work up, "
If we could mindlessly follow a book, what would be the point of starting low and working up, what would we be looking for?
"but if you can't believe the guide what good is it?"
No guide is any more than a guide and all are good guides. No offense meant, but we have to OBSERVE, and THINK!
"Whats your favorite manual?"
I have something like 20, 25 manuals (been doing this a long time). Got them maybe one every couple of years, mostly for new powders and new cartridges over the years. Don't really have a favorite, they all offer something, none is the "be all, end all." For noobs, I recommend Lyman. Or Lee.