With an Axe-Fx or any modeler for that matter the question is always going to be "connected into what?" Because Axe-Fx -> cab sims and FRFR is going to sound very close compared to tube amp -> loadbox -> cab sims and FRFR. But if you do the other way around and go Axe-Fx -> poweramp -> guitar cab the poweramp will be an important factor in how close it's going to sound like the real amp.
To me the Axe-Fx -> poweramp -> guitar cab setup is just not worth it because you lose a big versatility aspect, the cab. I find that many of the models will sound surprisingly similar if piped through a real guitar cab whereas with cab sims you tailor the cab to the amp, sort of like pairing the right speakers to a real amp. While a small FRFR won't sound like a roaring 4x12, it still is better at turning into different speaker models.
But by all means if you find a model in the Axe-Fx you like then the real deal might sound very close, taking into account Fractal does not model the same master volume tapers and uses idealized tapers for other controls so like for like settings are not likely to sound exact. As an example the Cornford MK50 model in the Axe-Fx is one of my favorites but having played the real deal, it was incredibly loud and just completely impractical for me. In a similar vein I don't see myself buying a Mesa Mark because I would have to compromise on the graphic EQ since you can't just flip a switch and choose a different setting like you can on an Axe-Fx.
But I got to say, there is something to seeing that tolexed box and having immediate, simple control over your settings. I really wish Axe-Fx had better MIDI knob controller support to make something like this work better.