I think it's very much a personal preference matched to your shooting style.
With a two-point, I mount the sling at butt stock rear utilizing the stock's existing rearmost sling slot. Up at the front of the fore end, I attach where a military M4/M4A1 would feature the factory sling swivel. Like in this photo (Old School sling back in early 2002 Afghanistan; a time before today's excellent commercial combat slings):
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I've never been fond of QD attachments. I've seen too much Murphy stuff to truly trust them.
Not around water ops these days to where I might benefit from the ditch-my-weapon-in-a-hurry option. Many slings today come with Fastex quick release buckles that suit that purpose anyway. I just never found usefully routine need for the QD click attachment feature. If I wanted to put the gun down, I just unslung it from my body. Sling stayed with weapon instead of with me. Not against them, just never needed them.
With a single point, I normally attach just behind the AR pistol grip, to an added receiver plate sling adapter. Like these:
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In the below picture, the attachment location for my single point is that visible silver ring (attached to a GG&G receiver plate) where the buffer tube joins the receiver:
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Blue Force Gear offers wire loops that are useful if you anticipate high rates of fire (and nylon melting barrel heat) while attaching tubular nylon, webbing, or paracord to a front sight base, barrel, or anything else that might get real hot). It also allows you to attach odd slings to odd places on odd weapons.
The Universal Wire Loop attaches a firearm sling to an AK, M4, M16, SIG, SCAR, a buttstock, or an eyelet - it will attach to almost any rifle - even an M240B machine gun.
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