One of the issues with FRFR setups is that suddenly, everything after the amp matters and becomes a variable you can change and therefore have to consider. With a poweramp and guitar cab, you have one amp and one cab. Done. Whatever it sounds like is just what it sounds like. AND, due to the directionality of guitar cabs, if you don't like the tone, you can just move your head a few inches around the room and suddenly your tone is entirely different and you get to tell yourself THAT specific head-sized sphere of area in your amp room is what "amp in the room" tone sounds like.
With FRFR though, suddenly you are in control of a virtual poweramp and you can use any IR under the sun, along with whatever post-cab or post-mic effects you want. Most players used to traditional amp-in-the-room setups have never really had to give much thought to stuff like mic placement or what cab+speaker+mic setup out of thousands they like best.
The other thing is that if you go FRFR, it would be a good idea to put at least as much resources into what FRFR speakers you go with, and mental resources into the IR you use, as you would a real cab. There are players out there who proudly say FRFR can never sound as fulfilling as a real cab because they tried out FRFR on a $75 pair of Chinese budget PA speakers, using just whatever IR happened to be loaded up. Of course that's not going to cut it.
But if you get good speakers that sound good to you, things start to even out. Also, going FRFR means you get to start learning about the differences between speakers, cabs of different manufacture, and all the popular mics. It will teach you so much you didn't know about guitar tone, and besides that, it's just a fun process.
Personally these days I would actually rather play guitar through my FRFR setup than my 4x12 cabs, as I think my monitor setup just sounds better, because I did my homework and figured out what FRFR speakers I like, along with what virtual cab solution sounds best for what I'm trying to do. Also, now my tone is transferable, meaning when I record it, it sounds exactly like what I hear it in the room. That's pretty much impossible with guitar cab in the room tone.
