Well you will get different opinions on this. Traditionalists insist on chrome-lined, and for good reasons. They are the gold standard. If you have high-use rifles in high humidity areas, it's pretty much a requirement.
However, with that being said, the new finishes do work. Especially if your firing schedule isn't that heavy and you don't routinely patrol in swampy areas. I've had several BA bbls with QPQ finish for over 4 years now and they have worked out just fine. No corrosion issues, even though I live in the deep south. And do a bit of woodland patrolling.
I recently switched one rifle to a BA 10.3" "Crane Spec" bbl, with is chromed lined, so now I'm running both, side by side. So I would say if you're building a "MK 18" type rifle, then get the "Crane Spec" bbl, which just happens to be chromed-lined, and drive on. If I was building another 14.5" model, I would probably buy another BA QPQ bbl.
This is just one man's opinion. I have had good luck with BA bbls in general and think the new finishes are going to prove out to be a valid alternative to chrome-lined. But you could say the jury is still out on that one. So chrome-lined, sure bet; QPQ probably gonna prove to be good.