6.5 will be more accurate by far in comparison to .308, especially with much less kick. 6.5 is one bad ass round....I would only get the 6.5 if you're going to be reloading. As for factory, most times than not 6.5 factory will be more expensive than .308 ammo.
as for reloading, about the only downfall is getting the brass,,,, and maybe somewhat the bullets depending on current supply. 6.5 brass is hornady specific, but other manufactures are coming out with the same brass & you can re-neck other types of brass if you want to go through all of that BS.... They have good stock of 6.5 bullets at my local big box dealer. 6.5bullets are a tad bit less than .308 depending on the style of bullets. As for example, 6.5 amax bullets are just a tad bit less than .308 amax, but not much. Once you have the brass, then you will save money as it will take less powder also.
like I said before, it really is about the brass.... 6.5 creedmoor hornady brass is going for $34.99 per 50pcs = ~ .70cent each. Once you have the brass, then you will save on powder and a little bit on the bullets. Primers is a moot issue.
as for .308 brass, I can get 500pcs of once fired lake city for $120 shipped = .24cent each,,,,, but will take more powder & will be just under the performance of the 6.5round.
Which caliber is better .308 or 6.5? Which is cheaper to buy and reload.