As I understand it, there is no advantage at present time. 6.5 Grendel was patented by AA, which limited who could produce barrels chambered in the caliber. The workaround for barrel makers who didn't want to honor the patent, was to come up with minimal changes to the chamber dimensions and coin it a different name, like .264LBC or whatever. In this way, they could ream Grendel compatible barrels, without risking lawsuits from AA, because its technically not a "Grendel." Now that SAAMI has adopted the 6.5 Grendel, its a moot point. I don't believe you will really gain or lose anything with variant chambers. Accuracy will be a function or barrel maker and quality. Buy what you can afford. I have a Satern 6.5 Grendel, and it shoots 0.5 MOA. I've heard you can buy economical and accurate barrels, which all seem to really be expensive compared to 5.56, but if buying some of the discount brands, you're going to be rolling the dice and will likely end up negating the inherent accuracy of the cartridge and thus not be impressed.
65grendel.com has lots of good info on the subject.