I was a 6.8SPC guy since they came out. I got in on one of Bill’s first releases for the Grendel, then got some of the first 264 LBC barrels Les made too, so I wasn’t only eating on the SPC side of the fence (and yes, I was one of the guys kicking and screaming about the Spec I vs. Spec II when all that BS was going down). I ran the numbers, did the side by side long range comparisons, took game with both, and I kept landing on the side of the 6.8 SPC...
Until the last few years... Now I’m a convert...
Now, the availability of components and QUALITY of those components strongly favors the Grendel. I still have three 6.8’s, but I recommend anyone buying/building a rifle now to buy/build a Grendel over the SPC. I don’t see any reason to expect a resurgence for the 6.8 - it won’t die, but it won’t boom again. The Grendel has a strong lead in the market, and if the Grendel shrinks in popularity, the 6.8’s niche will shrink even faster.
Both are great, but if I were starting over, it would be with a 6.5 Grendel. Or maybe even better, a 6mm variant of the Grendel.