Relevant to this topic I suppose: last week I brought my AFX3 to my friend's studio, because he's a big tube amp guy and I wanted to A/B it with him to show that it's identical in tone, and thus I am the more supreme human being in all matters and his studio and land will be mine by right of ancient custom. He frequently uses one of those IR loaders in place of a cab (I've never used one), so the plan was to just disable the cab simulation and use that. Anyways, once we got started I realized I was woefully unprepared for the A/B, and it took us some time to get a good setup going as I hadn't even considered which outputs to use and how to make sure the test was equal. When we ran the test, we found the tones were almost identical, however, the real amp was a bit more raw sounding with a little more output to the cab, but most of that difference, to our ears, came from a significant low-mid boost the Axe's tone had in comparison which allowed the mids of the real amp to come through a little better. Everything else was indeed identical in tone, and his conclusion was that he liked both individually and would ideally use them for different purposes.
Anyways, I wish I had posted in the community beforehand to make sure I had the A/B test setup correctly, because I don't feel that I got my big "they're identical!" or "the Axe is clearly better" moment I was hoping for. The most obvious explanation for the differences is that there was a combination of the amp models not having the same exact components (the amp used was the 5150 Blue 100W, but there's only so much I know about amp models, and I neglected to investigate just how different the A/B models were) and the signal levels not being identical altogether - which I can guarantee was an issue because we struggled with it for a bit. But either way, it was the first time I'd heard the AFX side by side with a real amp, and even with the differences (likely setup error) you would never be able to tell one of them was a modeler, which was a really cool experience altogether.