Of the 4 you have mentioned, I would go with the 6.5x284.
Both for selection of bullets and brass.
Your likely already aware, but that choice is still considered through the filter that you roll your own ammo.
While one can get it commercial, it is not usually at the countryside gas station, that you would find the more standard fare.
For that matter, 25wssm is limited as well.
I have not shopped for 270 of either version.......
If firearms resale ever was necessary, I would think that would be a check in the favor of the 6.5 as well.
“When a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty to throw off such governments. …” Jefferson
We are very close to this point now.