I've had a half-dozen of each. The velocities I've obtained are fairly close, and not enough to make a shooter choose one over the other, frankly.
One peccadillo I HAVE really noticed though, is that every .257 Roberts I've owned (2 Brownings, 2 Rugers, 2 Remingons, 2 Winchesters) were finicky to load for.
Every .250 Savage I've owned (six 99's, a Savage bolt and a Remington bolt) was dead easy to load for.
That said, the fact that I still have two .250-3000's and a .250 Ackley doesn't make me stop wanting another Roberts.
I've had 5 factory barreled 257 Robs, and all were picky or mediocre accuracy-wise. That's not to say a finely accurate 257 factory rifle isn't out there, I've just not had one.
Have only had one 250 Savage, a Ruger 77 RSI, so a sample of one isn't that impressive.
BUT, about 20+ years ago I was planning on a custom 250 Savage on an M70 action. I decided on an HS Precision cut-rifle barrel for it. I called HS, and somehow got the shop manager on the phone to discuss my project. He was obviously busy and really didn't want to talk, until he asked what I wanted the rifle chambered for. I told him "250/3000"... then he wouldn't shut up! He waxed absolutely lyrical about the 250 Savage, and told me over the years it was the most consistently accurate round they chambered for. To me, that's saying a lot. Really, the 6.5 Creedmoor is just a blown out, slightly upsized 250 Savage, and I think we all understand there is some "inherent accuracy" in that general design that it shares with the 250 Savage. Really, it's mostly the 1-14 twist that messed up the Savage.
I love the little 250 Savage. Maybe Larry Koller's books had something to do with it, but it genuinely "kicks a little and kills a lot."
