RCF310A or Matrix QA12 ?

Why do you think there are advantages at all? How do you like your cab?

Generally speaking: All FRFR cabs claim to be full range and flat response as an ideal.
The better ones don't deviate too much from this ideal, the lesser ones will.
This can make a difference.
The Matrix is quite flat so it won't give you any more 'guitar cab experience' than any other good FRFR solution.
Also I don't get what you mean by your RCF being t'oo hifi'.
Hifi comes from high fidelity and originally intends to achieve the same as the newer term FRFR.
Ideally the sound out of an RCF, Yamaha DXR, Atomic CLR Or Matrix Q12a should sound exactly like your miked cab. If you don't like this you should try a conventional guitar cab.

I think in this case you need to do a side by side comparison to see what you like better.

You're right, the differences are definitely there but indeed they are not spectacular.

You're welcome.

I tried out a few FRFR Monitors and finally ended up with the RCF 10" active Monitorbox (at least my band uses a complete RCF-P.A-System, so this has additional advantages).
In my experience it is as said, no solution fitted my needs exactly, but the KPA was capable to be tweaked to each Monitor-Type. So IMO it's only a matter of dilligence (i.e. listening tweaking listening again a.s.o.)

Compared to a real guitarcabinet the FRFR-Solution IMO leads to better results for the audience, for the guitarist it can be challengeing because of the necessity of changing paradigm. Although the Direct-Amp-Profiling feature now combates again.
Things won't become boring .........