Either will get you to 1000 yards Smithy.
I'd go with the 300 Win myself. You'll get better barrel life and have a much larger selection of brass as well. Plus you won't have to deal with the double radius shoulder on the 300 WBY case. If your a reloader, you'll grow to appreciate the benifits.
With that being said, I do have a 300 WBY in the safe, but no 300Win:confused: