the 6.8 SPC round. Like some have already stated, out to about 300 meters, it's hard to beat, as far as accuracy, recoil, and energy. Past that, then you might want to look at other options.
But getting very many options for loads/rounds is still a bit of a challenge. Unless you load your own, you are pretty limited on selection on either, with the vote again going to the 6.8 SPC for variety.
Another option, is the 260 Rem (a 6.5 Grendel in sheep's clothing), along with about the same results in variety of ammo.