Some times cost comes with nothing more than piece of mind, but not every time as cheaper options can be just as good.
Outside of the basic phosphate coating that comes standard, the only measureable difference between that an Nickle Boron, black nitride, and Titanium nitride are their improved “cleanability”. I’ve run a variety of both and as far as I’m concerned the notion that these coatings ad some form of lubricity is just ludicrous. On a microscopic scale, on paper yes I’m sure they do but in reality and in my personal experience with all of them, there is zero measureable or noticeable difference.
I’ve run in my personal rifles, basic no name Mil-Spec, LMTs, Colt USA, Colt Canada, Lantac NiB, AAC NiB, a misc TiN that I can’t recall the brand, BCM, and a Noveske Black nitride, non of which performed any better or any worse than the competition.
The only concern I would have is wether or not the manufacturer had a reputable history of making parts that don’t break (unlike NEA/BCL that are prone to catastrophic failures), and that the gas keys are staked correctly. Outside of those two things, buy whatever jingles your jollies.
For what it’s worth, after all the rifles and parts I’ve sold off this year, in the two remaining rifles I own I have 2 BCG’s.
One is a BCM in their tan phosphate colorway, and the other is a black nitride Noveske BCG.
Want to know why I have those two? Because I have a BCM rifle and a (mostly) Noveske rifle. Literally no other reason than that. Both reputable companies known for a history of quality kit, and because it jingles my jollies having mostly matching manufacturers in my rifles.