Wow, I missed the fun....

Poor OP, seeing us old farts argue in circles.

One point that some might argue about, but few have personal experience with, is that the elite full susp XC bikes are a different animal than many other XC bikes. The Yeti ACR (might have gotten the letters wrong) and the higher models of the Spesh Epic can hold close to a hardtail in climbing, and provide to advantages (line choice is more open with suspension).

I have ridden both, many times, on the same trails. I have no doubt, based upon my Garmin watch, that the trail makes a big difference upon which bike I can ride faster. However, I am far from an elite rider. I do believe my 30+ years of mountain biking, though, provides me some reasonable perspective.