Let me cut to the chase and say I agree 100%+ with this:
I use a coyote brown Spec.-Ops. "Patrol Sling" (#101030111). It can be mounted in several ways, including single-point on most rifles (it´s not a dedicated AR-sling). The quality, workmanship and ergonomics are outstanding. I highly recommend it! IMO the best two-point sling on the market and decently priced too.
I own four of the Spec-Ops patrol slings and I consider them about the best value on the market for any kind of sling. They can also be used as a 1-point, but are really designed for and better suited as a 2-point.
Single point are the only way to go if you are actually going to do any shooting with an AR.
I absolutely disagree. Single point slings do work great for shooting around barriers, shoulder transition and CQB. Start walking and they are pretty bad. Drop the gun to do a handgun transition or do anything with your hands and they're awful, and you'll understand the recommendation to wear a cup. Drop the gun from a kneeling or crouching position and a muzzle strike on the ground is guaranteed.
Basically I see AR sling options as this:
-single point: CQB only, good for that but not versatile. Also may hang up in gear (chest rigs especially).
-two point: most versatile. Not as good for shoulder transitions or for walking 10's of miles, but OK for both, and truly the happy medium and best balance. There's a reason most of the experts and trainers have gone to them.
-three point: considered obsolete by some, these should not be ignored. They are a bit complicated and generally worst for shoulder transitions, but provide very comfortable carry (especially patrol carry) and outstanding control of the gun. They can hang up in gear and can interfere with the safety lever or other left-side controls, however. A good choice for someone who is walking extensively and using the gun little, or will always have at least a few seconds to go from carry to firing.
As for brands, I think Spec-Ops is outstanding regardless of price and is even better when their reasonable prices are factored in. For two-point designs, the Blue Force (Vickers Tactical) and unrelated V-TAC slings are generally seen as top options, with Specter usually mentioned right behind. I don't know why Spec-Ops isn't mentioned as the very top option because based on all the brands I've used they have the best materials and construction, with the design of the Patrol Sling being only slightly behind the Blue Force and V-TAC (which do have a slightly better design for adjusting length). Many spec-ops slings offer multiple usage options, with the "T.H.E. Mamba" being able to be used as a single-, two-, or three-point design just with the included pieces. Likewise, the patrol sling works as a single- or two-point sling in stock form.