I've never cleaned an AR barrel with anything except a Boresnake. My used and abused BCM 14.5 will still pop 8" steel at 400Y all day long.
I finally bough a free-float rail this year, a BCM KeyMod.
"For a moment he felt good about this. A moment or two later he felt bad about feeling good about it. Then he felt good about feeling bad about feeling good about it and, satisfied, drove on into the night."
-- Hitchhiker's Guide to the Galaxy --
I'm generally a fan of Magpul stuff, that was the main deciding factor when I went with the M-Lok handguard for my carbine.
One thing that sucks is that I bought an RVG M-Lok adapter and now they've come out with a direct attach RVG and AFG. I'm really liking the looks of the direct attach AVG, will probably end up picking up one of those.
I like my KMR rail as its done what it's supposed to do very well. I don't accessorize like Barbie so all I have is a BUIS and stubby VFG on the gun. Eventually it will get a light, but that's about it. Next handguard for the wife's unit will be an ALG MLOK jobber.
From a technical standpoint both KM and MLOK will get the job done. The winner will most likely be based on supply chain. Who will be able to get accessories available at your local LGS? Who will have the most variety of goodies? That is what will become the deciding factor to most shooters, the rest is all mumbo jumbo to the majority of AR owners. On that front I think MagPul has the advantage.
How does the mounting system on the Centurion CMR fit into this mix? Seems to be a proprietary option. That had been my pick for a new build, however MLOK/KM have given me some pause on this.
As an aside, it seems odd to me that KM might not be the winner given BCM somewhat recently came out with their KM compatible rail. Either they are just making a bet on which way the market will go or the wind changed from the start of R&D to the product hitting the market.
Mlok offers a number of advantages over KM, and I think the market will respond by filling in the gaps where KM is currently ahead just because it has been available longer. ML has made very quick inroads as it is.
That said, I still don't mind lightweight quad picatinny rails. DD has been doing them right for years. Their newest "M4 Rail" is nearly as thin as a tube, doesn't require adapter rails, bolts up with a lot of strength and is about the same weight when you factor in adapter rails and hardware.
In general, I find purpose built quad rails to be more sturdy than modulars/tubes. This makes a difference with barricade shooting, bipod loading, and just overall durability of the rifle. Geissele rails and a few others are the exception, in my experience.
Now, all that said I think the one of the best options going is the ALG Mlok tube. It is stupid light and stupid cheap. The barrel nut is huge and offers more stability than many other tube rails. I don't know that it's an SPR w/ bipod type rail, but for a short, lightweight, 1x optic type rifle they are great.
For me, direct attach is a must with either KM or ML. There's little point in having this fancy modular attachment if you just have to bolt on a piece of pic rail to mount what you want. The market is getting there.
The opinions above are my own and do not represent any current or former employer.
I guess I would ask you if shooting 20,000 rounds though the same gun/barrel is something that is an important/realistic consideration for you? Or is it a "nice to have" thing vs. a "need to have" thing? I can be convinced, but I currently have the same opinion on CHF for my purposes as I had before.