I have a couple of rifles with about the same specs as your build and I like them enough to keep them around.
Although I have a few dozen rifles chambered in 250-3000, I prefer the 25 Souper in short actions as it provides a little more performance than the 250-3000, approximately the same as the 250AI and 257 Roberts. That said, if you're willing/able to limit your reloading to bullets in the 75 to 110 grain range, the 257 Roberts doesn't run into COAL issues in a short action like it is prone to do with heavier/longer bullets.
If you have a choice of rates of twist, you might as well go with a faster ROT so that if somebody decides to make VLD .257" bore bullets, you'll have a barrel that will stabilize them. Otherwise a 1-10" ROT has been the standard in the 250-3000 for the past 60 years.
Good luck with your build and remember that since it is your build, you should build the rifle that you want, not the rifle that someone else thinks would be better for you.
