I have a 260, but bought it because it was a bargain and not because it was that caliber. I've come to really appreciate the caliber and I'm a reloader. One thing the 260 has in its favor is the basic cartridge case. As long as there are 243, 308, 7-08 cases around, I'll be able to get brass. There's hardly anything more common than 308 based cases. So if I didn't have a 260 and was looking for a 6.5mm cartridge, I'd probably rank the cartridges in degree of desirability like this:
And if I needed more horsepower than those offer, and I couldn't get it with the 260 AI, I'd probably go for the 6.5-284, the 6.5-06, and then for the belted mag. I'd still worry a small bit about the avails of the 284 case. Winchester still makes it, but hardly anyone still shoots that round, so the 284 case is most in demand for wildcats off that case. That doesn't lend itself to longevity like a 308 based case does.