I read the first page, including your OP, then skipped to here to make this point. Apologies if it's already been made.
You said in your OP you're a handloader. With that in mind remember the 30-06 is a 60K PSI cartridge and the 300 WSM is 65K PSI. Load both to the same level and the "not-too-great-already" differences in performance get even smaller. Nosler lists the water capacity of the two cases when loaded with a 180 Partition as 63.9 gr and 71.3 gr respectively. Using the well validated ROT that velocity potential increases at about 25% of capacity increase, that means (if pressures are equal) the WSM has only a 2.8% velocity advantage over the -06.
5 in the magazine, vs. 3, etc. etc.
But the 300 WSM with its "short-fat" configuration might be more "inherently" accurate, though we all know the -06 is a very accurate round. Since SPS got in a boat load of 200gr Partition blems I have become enamored of this bullet, with its (measured!) BC of .501 and 2650-2700 FPS potential from the -06 (at 60K PSI). I laid in a lifetime supply. The nums on that are most impressive when you run them out at range (and of course the nums on a WSM would be even better - more the question is what's enough) 2000+ fp at 400 yards and less than 9 inches drift (10 MPH cross)
I love the -06 but both are great and you should build what you like/want the most.
Enjoy the process,
Rex
