I looked up some balistics (I have always been a fan of 6.5 x 55) Creedmoore does outperform the 6.5 Swede with lighter bullets; once you go 140gr + in bullets, the 6.5 Swede gives about a 100-150 fps advantage, and the co responding 200+ ft. lbs of energy. Yes, factory ammo is not easily come-by here; and there is not a great selection of rifles; but good rifles can be had. The 260 is similar; go over 140 gr. you get about 100 fps more and about 150 ft. lbs more energy... On paper...
In real life, there is not a lot of difference... so I will stick with my antique 6.5 x 55 ammo. LOL
BTW, no deer for me out at 1000 yards (on a good day I can almost see that far).