If there's a particular color that pleases you, you might want to paint your pictures on a canvas that already has a hint of that color. Then quasi-FRFR is right for you.
If you trust your paints and your color-mixing ability, you'll want to paint on a canvas that's as white and neutral as possible. Then you're a FRFR guy.
Rex, that's a pretty good way of looking at things.
To build on what you've said, I suggest that the other requirement for quasi-FRFR to be effective is that it be your
only source of sound. That is to say, it's effective when used as a backline (i.e. no Axe-FX direct feed to FOH) or in a home studio where it provides all your guitar sound.
This brings up an important concept, and perhaps another new term we can adopt. . .
"patch portability". A significant advantage to using FRFR is portability of tone. To build on your colour analogy, there are tools and standards used in printing and photography that are designed to ensure consistency of colour. Monitors are calibrated so that my green and your green are the same. Printers are profiled so that the yellow sun on my screen prints with the same shade of yellow. Pantone has an extensive catalog of colors that are named and specifically defined. This is all about portability. When a company selects a colour for their logo they can be confident that it will look, for all intents and purposes, the same in an annual report as on a billboard.
Patch portability is all about ensuring, within reason, that the sound I spend hours crafting in my studio is the same sound the crowd hears through the FOH at Friday night's venue. The way to do it is to develop that sound on a calibrated system. A good studio monitor in a properly treated room is one (common) calibrated system. If my Friday night gig is played in a decent room with good speakers, EQ'd to accommodate anomalies, then my tone should translate reasonably well. If I monitor my playing on-stage using a CLR, or another high quality FRFR system, then my tones will be essentially the same. Maybe I decide to switch to in-ears along the way. If I pick up reference quality in-ears, I'll be good-to-go. The key to this working, and to patch portability, is starting with tones crafted on a reference system.
But real life is not like that, you say! No, a lot of venues and their FOH installations are less than ideal. Or, one set of in-ears may sound different than the next. One key to success in an imperfect world is to limit the number of variables. If I develop my tones on a truly neutral, reference system, then the only equalization required is what's necessary to account for the difference in that venue. However, if I've developed my tone on a quasi-FRFR system I have TWO sets of equalization's to do. One to account for the imperfections in the venue and a second to dial in whatever "colour" my quasi-FRFR system has imparted. The chances are good that dialing in that quasi-FRFR "colour" will be complex. Just think about how complex a speaker IR has to be to capture the colour of your favourite monitor. Have you ever tried using EQ to simulate a speaker IR?
So. . . I can see situations where quasi-FRFR can be desirable. The key IMHO, is understanding the limitations of that approach, and using quasi-FRFR wisely (i.e. within these limitations). FRFR solutions on the other hand IMHO, do not suffer from these limitations and as such, produce better results across multiple venues and output devices, with less effort.
Terry.
