Re: new stick, what caliber???
Aside from kindling additional domestic interest in the 6.5mm bore size, I don't see a ton of advantage in the newer round. If I already had my reloading setup for the .260 (and I do), I would see the new chambering simply as a complication. If I did not, I'd be strongly tempted to make it my first, maybe only, 6.5mm chambering.
Having said all that, I agree with Rob01's excellent writeup. I appreciate the longer neck, and have genuine confidence that it combines with the slightly smaller case capacity to prolong throat life IF one resists the temptation to hotrod the loads. Not by a lot, but probably by a measurable difference.
In a competitive environment where the 6.5-284 has a significant LR advantage over the .260 (IMHO), I have to question why one would choose another, marginally more anemic, version of the same thing as the .260. In its own rite, the .260 is an excellent all around cartridge, but for LR comp, it just gives away too much to the 6.5-284 to rule the range. I suspect that much of Rob's success is due to his own superior individual marksmanship, that he could do as well with a workmanlike .260, and even better with a 6.5-284.
Greg