As noted, it's the equivalent of the 6BR, but designed to work in the AR platform.
I had a Savage LRPV rebarreled in 6.5Grendel, and it was a 0.3MOA gun. I passed it on to a friend who likes oddball calibres.
I have an XCR that I had Ian at Herron Arms make up a shorty barrel for in 6.5Grendel, and it's as accurate as you can get in that platform.
6.5Grendel ammunition is pretty scarce, and the demand, and therefore supply in Canada, is not going to get any better in the foreseable future.
I don't see any advantage of 6.5Grendel over 7.62X39, in the XCR platform.
I wouldn't recommend it in a bolt gun over the tried, and trued, 6BR.