Re: hodgdon extreme versus the others!
RL25 and H50BMG have worked the best for me in my 300 RUM tight neck.
I have not seen much temp sensitivity in the RL25 like some have. In fact I have seen my loads get a bit faster when it got colder.
Alliant and H powders are both excellent. Choose the one that works best for you and be happy. It helps to do temp testing with both loads. Once you have determined how much you will gain or loose for a given temp, you can then adjust your velocity accordingly for your PDA program.
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.