My only perspective with these is in basic cartridge design. I use way less powder than either to get what I need in my 6.5wssm.
The WM represents a huge case with 15gr more H20 capacity than the 6.5/284.
Larger capacity will always mandate more slower powder for the same velocity, but will have more velocity potential with the right powder & fill.
Don't be fooled by comparisons with same powders, as the optimum powder for both cartridges will be totally different.
Also, the good and bad of both should also be considered with more than one attribute(unless velocity is all that matters to you).
The 6.5/284 has given all neeeded in competition, but with a price of barrel life(always a price). Anyone could expect ~1200rnds accurate from it.
It's available brass, dies, reamers, etc, are excellent.
With the same shooting you will only get ~975rnds of barrel life from the WM.
Of course it's purely a hunting cartridge and that could be a lifetime of use.
I don't know about the brass quality other than it's belted and so I would have nothing to do with. Maybe someone will chime in & tell you how to make one worthwhile.
