Brass prices on the 26 are coming down. SPS has 140 NAB ammo for a good price, check it out.

I've not worked with the 6.5/300 Wby, but did spend some time working with a friend's .264 WM. I find the 26 Nosler easier to work with, more forgiving as long as one uses very slow, Vulcan type powders, such as 869, 872, etc. With conventional slow burners, there isn't enough difference, IMO. The 26 starts to really shine with ultra slow powders.

DF