And the 6mm has less recoil than the 257,
And the 6.5 has greater frontal area than the 257.
Minutiae! And you could hunt for a lifetime and never tell the difference in the field.
But if it turns your crank, carry on!
There does seem to be quite a few people that believe the .257 has advantages over other bore sizes, or at the very least, is different enough to justify owning one.
And I am one of those quarter bore nuts. Been shooting a25/06 since the early 60s when it was still a wildcat. For the last 30 years, my favorite deer rifles have been the 257R, 257AI, and the 25/06.
The point is, for me and 99% of hunters, improving the BC from .4 to .57 would make no significant difference . If you want to shoot deer at long range or targets at long range, go for it.
And since we have stooped to name calling, l guess we Neanderthals do giggle at you boys who have to have the latest and greatest. :-)