Which 1 is better? The one you already own would the best one. If you don't own any of them and are trying to make up your mind I'd advise you to get the .308.
It is proven (not like others aren't) and ammo is cheapest and easiest to obtain. And if you handload you will always find the components cheaper, especially the brass.
I own a .308, a .243, and while I don't own a .260..... I do own both a few 6.5 x 55's and a 6.5 x 54 (both pretty close to the .260). I personally would prefer the .260, but I believe the .308 is a best buy.