The 6.8 or Grendel do not recoil much more than a 5.56 and not near a 308. There are more factory hunting loads for the 6.8 and more usable hunting bullets in the correct weight range. A lot of the 6.5 bullets were designed for the 260 and 6.5 Swede, they will not expand at slower velocity. Anyone that has hunted with a 5.56, 300, 6.8 and 6.5 can tell you there is a difference in terminal performance on game, especially hogs.
It's true that the 6.8 has more purpose built bullets and a lot more factory ammunition choices. Bullet makers had to make them in the 90-120 grain range because almost all 270 bullets are 130 and up.
The Grendel has plenty of bullets that will work just fine out to 300 yards. There was always a plethora of 6.5 bullets from 100-120 grains that will expand down to 1800 fps so there was never the need for Grendel specific bullets.
If you reload, you'll have plenty of options with the 6.5 Grendel or 6.8 SPC. If you don't you are much better off with a 6.8 SPC.
