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edited to add: I missed the last page of replies before typing this post, but I'm gonna leave it here for posterity anyways. And add this bit
How is it not relevant and how is that analogy at all applicable? He's saying a 600$ amp sitting in the room with him sounds better than a 3000$ modeler running a cab IR through an FRFR monitor. Thats not at all like comparing a tele to an LP, thats more (but of course not exactly) like comparing playing a tele yourself to watching your buddy play an LP. What he's trying to say is that Amp A sounds better than Amp B when both amps are in the room being played next to eachother. What he's actually saying is that Amp A sounds better than Amp B when Amp B is being recorded in a sound-isolated booth and you're sitting on the outside listening on headphones or monitors.
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I'm pretty sure at this point that you've gotta be a troll. There's no other possible way that you've had this very simple idea explained to you so many ways by so many people that are trying to help and you still refuse to accept it. But I'll bite and try this one more time.
Our logic does "stand up to basic questioning." Its yours that absolutely does not. The reason the axefx can simplify your rig is because you can send your signal direct to the FOH (front of house) mains without needing to mic up a cab. The trade-off in that scenario is that you don't have a cab on stage, so you rely on an FRFR speaker, stage monitors, or in-ear monitors to hear yourself playing. None of those monitoring solutions will ever sound or feel like an actual guitar cab sitting behind you on stage. Thats not a flaw or shortcoming of the axefx, thats the way that two very different systems work. Gigging musicians who understand this concept use an axefx so they can show up with a 2u rack and a foot controller, plug one or two cables into the stage snake and be done with setup. They understand that the traditional cab on the stage is only for them, that the audience doesn't hear it anyways, and that they can get a cleaner, often better sound out the audience by running direct. If you take that ac15 to a gig, the soundman is going put a microphone in front of it. He's going to tell you to turn it down quieter than you want it so that your amp isn't projecting much/any sound off the stage and into the audience. He's going to EQ that microphone signal so it sounds good in the venue and he's going to amplify that through the FOH mains. If you stand in the audience during that gig, you're going to hear the sound coming from that microphone, not the sound from that amp sitting in the room. If you put THAT sound on the left side of the stage and then put an axefx with an ac15 model & similar (good) cab IR running through the right and then stand in the audience, the sound is going to comparable.
You continuing to sit here saying a tube combo amp is somehow objectively better than an axefx because it sounds better in the room than the axefx does with an frfr setup is tiring and frankly asinine. If your use-case for an amplifier or the axefx is such that you'd enjoy a tube combo amp more, then by all means, go buy a combo amp and cart that around to play with. Alternatively, spend anywhere from 50$-1000$ on any plethora of options for poweramps (I've had good luck with both an EHX Magnum .44 for ~100$ and a Matrix GT1000FX for ~600$, depending on the volume needed) and a decent 1x12 cab and run the axefx that way. Then you can still utilize the whole library of amp models plus all the effects and everything else.
As far as trying this setup out using the ac15, the best you can do is plug out1 into the regular input (not the top boost) of the ac15, set all the tone controls to noon, set the gain so that its as clean as possible and set the master volume to taste. In the global menu of the axefx bypass poweramp modelling and cabinet modelling then pull up your ac15 preset and see how it sounds. It won't be perfect as there will be extra coloration from the ac15 preamp section, but it should give you an idea. Or, find someone who has a rack poweramp & a cab or any amp/cab/combo with an fx loop and plug into that.
In summary
[tube combo amp =/= axefx into frfr] therefore, these two setups can't be directly compared
[tube combo amp = axefx into poweramp and cab] therefore, these two setups can be directly compared
[tube combo amp mic'ed up at a gig and listened to via monitors or FOH speakers = axefx into frfr or listened to monitors or FOH speakers] therefore, these two setups can be directly compared