I'd suggest the .308 and the first reason is, there are no "brush guns" that I know of made in 6.8mm. Other than that the .30 caliber will offer heavier bullet choices for hunting purposes. There are very limited factory loads for the 6.8mm and it's harder to find ammo for anyway. If you are reloading for the 6.8mm you will have more choices, but it doesn't have the power or versatility that the .308 has. You may also consider other popular "brush" choices like the 30-30, .44 mag and .35 rem.
A really short rifle of a handgun because they easier to carry through heavy cover. I've yet to find a hunting round that won't be deflected by sticks. As soon as you interrupt the gyroscopic stabilization of a bullet, off course it goes. (see Matt g)
God, Family, Guns, in that order.
If you are looking for a hunting rifle, I would go with the 308. You'll be able to shoot anything the 6.8 can weight wise and then some. The .30 rifles have been around so long there are more options for loads then almost any other.
If the pain is lacking so is the discipline...
"the only 911 call I need is chambering a round" - Mr. Muller, MO car dealer