.223 at 1000 yards? I can only imagine what a breeze of wind can do to your bullet at that range. And I personally think the .223 is an over rated round, every AR nut loves it though. And where are you located, this is the first I'm hearing the .308 being underrated.
Personally, I think the .243 is underrated. But it's a flat shooter. Also does alot of damage for a bullet so small. I don't like ARs, but if was going to buy one, it'd have to be an AR-10 in .243. I do not understand the .223 craze. I had a rifle chambered for that when I was younger, I didn't like it.