There are several barrel profiles available. Standard (light weight), heavy and full profile heavy. The standard light weight barrel weighs about a pound or so less than the heavy. Long range accuracy may or may not be up to that of the heavy. The standard will heat up a bit more quickly but is A LOT more comfortable to carry around.
The heavy barrel is heavy from about the gas block to the muzzle. It is more muzzle heavy and some like this feel. They will not heat up as badly/quickly as the light weight.
The full profile heavy weighs another pound or so more than the heavy. Very cumbersome to carry but very solid. For a designated marksman's rifle it is pretty nice. To hump all day is a PITA.
It kind of comes down to what the intended purpose is for the rifle. Is it going to be carried a lot and shot a little at shorter ranges (under 200 yds)? Go with the light weight. Is it going to be carried some and shot more and at medium ranges? Heavy. Are you going to hunker down and pick off targets at 300+ yards? Full profile heavy and at least 20" length.