I have a 257 wby in a factory MKV. The only thing done to it was a custom stock and bedding job. It shoots a legit 1/2 +/- moa. I also have a 6.5x284 Norma custom that shoots bugholes. It's not necessarily one of the new hot rod 6.5's but it's a 6.5 none the less.
I've used both rifles on deer sized game out to 500+ yards. Now with that said I realize that's a chip shot for many of the more skilled people on this forum and I respect that. I'm just not comfortable with my capabilities shooting game further than that yet. However, none of the animals I have taken argued either way about a super mag or old school. With the weatherby I would still be a little less apt to try a much further shot only because of the lighter weight bullet offerings. Perhaps when I put a longer barrel on, with a custom chamber, I will be more confident with a bullet heavier than the 100gr TTSX or 110gr acubonds I've been using. With the Norma, it's a no brainer using the 140 grain bergers. That particular bullet has proven itself to a distance a lot further than 500 yards with many other hunters and target shooters.
Last year I was in Montana shooting steel with a very knowledgeable man who competes in sniper matches at a national level. He shoots a 6.5 SAUM. He loves the caliber and told me that because of the velocity that round cranks out, he has a minimal amount of adjustments he has to make when shooting a timed course. But my Norma, shooting over 200 fps less, with the same 140 Berger, made it to the same steel targets. Only difference, of course, was the drops and windage. Long story short, I'm not arguing either way. I think what works for you and your hunting needs is all that matters. Pick what ya like and enjoy yourself.
Best of luck,
Erik