I shoot both the 6.5 Creedmoor,and the Remington 260. Both are great calibers ballistically. There's really no difference between them in their performance,but each has its own +'s and -'s.
The Creedmoor really shines with the long match style bullets.This caliber was designed for them,and you still remain well under maximum overall cartridge length for almost any magazine-Bolt action or Semi auto magazines.Using the same type of bullets in the 260 Remington usually means loading them one at a time if you want to set them out towards the rifling lands.
Factory ammo is available for both,but the Creedmoor is easier to find,and usually cost less than the 260.
The negative on the Creedmoor would be the brass. Hornady brass is fine with avg power loads,but step it up a little,and the primer pockets will get large quick-2 or 3 loadings. Nosler brass is about $1.30 a case-$64.99 per 50,so that really hits you in the back pocket over the Hornady-$34.99 per 50.
I'm also using 22-250 brass,and resizing it to 6.5 Creedmoor.I just don't have much data yet to see how many loadings it will get.
The negative on the 260 Remington is also the brass,if it's Remington brass. I have never had much luck with any brass that has a Remington stamp on it,the necks are just too thin,and they split after a couple loadings. But,with the 260,I resize 243 brass,and so that doesn't ever come into play with me.
My 260 Remington is a Semi-auto DPMS LR-260H,so I only load the bullets out to maximum magazine length of 2.810. It shoots the same bullets that I shoot in the Creedmoor,but the results are different.
Both calibers are very fun to shoot,and have very mild recoil,so someone that is small or recoil sensitive can shoot these calibers and shoot them good without developing bad habits from recoil issues.
Reloading for both is great,they both use the same powders.Before I was able to get new load manuals,after looking at some standard loads for the Creedmoor on the internet,I looked up the same powder/bullet combinations for the 260,and they were very close so I just started loading off the 260 Remington data until the new data manuals arrived.Note* Always staying under Max.loads,and always looking for pressure signs* I don't suggest this,but I've been reloading over 3 decades,and I'm very sure of what I'm doing.
Depending on the gun and the shooters ability,both calibers are very accurate easily to 1000 yards. Shooting sub-moa groups at 100 yards almost gets boring with both of the rifles I have while doing load testing.
I've tried everything from 100 gr Varmint bullets to 140 gr Berger Hunting VLD's with these calibers,and the love shooting almost anything I feed them.
If you want a good long range caliber,and also a caliber that will take down medium sized game,either the 6.5 Creedmoor,260 Remington or the 6.5x55 Swede will do the trick.
Here's the 6.5 Creedmoor I built-
Here,I was testing a new powder and primer with several bullets,in different rifles-