just a quick quote from Cliff:

I've compared the 11R, KPA, HD500, etc. and the Axe-Fx comes closest to the real thing. The 11R with the right IRs can come pretty close (but you can't load IRs into it so it's an awkward solution) but I can still pick it out 80% of the time or more. In A/B tests I can pick the KPA out every time. It has a signature to the distortion and pick attack that differs greatly from the real amps. I have had no luck getting the HD500 to sound like the real amp.

i just thought that it was cool that he mentioned the 11R as one of the better modelers of the bunch.