How far is "long range" for you? Out a quarter mile or so, the difference in trajectory between the 6.5 Creedmoor and 6.5-284 would likely be minimal, as the difference in muzzle velocity is around 150+/- fps, assuming all variables are equal.
In a short action .264" bore, I'd prefer the 6.5 Creedmoor and in a long action I'd prefer the 256 Newton or the 6.5-06.
I have four 6.5-284, but haven't shot any of them for awhile. I also have four 6.5 Creeds and have only shot one very much, probably 300 rounds, but it is an excellent shooter.
