That's a hard choice, really. Sure, the 7-08 has the higher BC bullets with good speeds, but you will not be able to use them at AR10 mag lengths. So, what's the better choice? That's the hard part. I have George's first ever GAP-10 in 308 he ever made, and it's hard to beat a good 308. If it were a bolt gun choice, it's an easy pick of 7-08. But in an AR-10, I'll take the 308.