If you want to know my experience... I bought a DPMS LR-308C (the 20" version). It was very accurate... it would shoot 1 MOA with surplus ammo... but it was too heavy. One thing I learned is to watch what barrel you put on these, as that is where most of the weight comes from. I personally did not want a bench gun... I was after a battle rifle that could be taken into the field. You may not care about this issue if it is a range gun only though.
I was not interested in less than a 20" barrel... I do not like the extra muzzle blast and flash, and I do a lot of long range shooting, so I don't like the decreased max effective range.
I found that if you want a rifle with a light profile chrome lined barrel that is at least 20" long, your options are pretty limited with AR's. The AR-10 is about it.
I sold the DPMS and bought an M1A, and am glad I did. The M1A is more reliable and dependable, much lighter, better iron sights, and is only barely less accurate (1.25 MOA as opposed to 1 MOA with surplus ammo, which is still more accuracy than I really need for the intended role).
If I were to build another .308 AR (which I'm thinking about doing), I would go with a Mega Arms MA-Ten receiver set, which gives you a DPMS-pattern mag well but lets you use either DPMS or Armalite pattern barrels and bolt carrier groups. I'd throw an AR-10 20" CL barrel on it with a DPMS barrel nut, and a DPMS chrome plated BCG, and Troy's new TRX Extreme .308 12" free float handguard. The whole thing ought to come out around 9 lbs. the way I figure it. Not too bad. I don't know that I would replace the M1A with it though... I would have to really put it through the paces to see what kind of reliability it has.
Let's face it... I am never replacing the M1A. It is stone cold reliable and has never let me down, even firing it filthy, the mud, in the rain, in sub-zero temps, whatever I throw at it... it always gets the job done. And I doubt anyone will ever invent any better iron sights in my lifetime than what comes on that rifle from the factory.