Keith,
If you're talking about the guns themselves, you talking about two very different animals; the AR-15 vs. the AR-10, SR-25, etc.. Larger, beefier and perfectly able to handle the heavier recoil of the larger round. AMU has been using the M110 30 cals as 1,000 yard guns, getting away from the 5.56s in M16s they've been using for years, and yet side-stepping all the inherent problems that go with the M14 family. Getting very good results too, from what I've heard thus far.
I'll be able to tell you a bit more down the road. Steve Satern set me up with a SS 1x10" barrel chambered for the .308 Win this past weekend, so I guess I'm building a new M110 1000 yard gun this season.