I know this isn't really relevant, because you're talking about a much higher-end rega, but I've had P3-24 with TTPSU, groovetracer subplatter (a huge upgrade), nice acrylic platter and tecnoweight on its RB303 arm. The cartridge at the time was Denon DL-110 going into EAR 834p phono stage. I was very happy with this setup, loved it.
However, there was a good opportunity for a s/h Gyro and I went for it. It was a version with newer, inverted bearing, new version of suspension turrets, orbe spindle/clamp and gyro platter and old AC motor with Gyropower PSU.
I used the same arm and cart from P3-24 into the same phono at first, so I could compare the decks well.
Tye differences, that were all obvious immediately, were that Gyro gave more texture and tone with everything. Microdynamics were much better. Resolution was better. Also, the deck sounded more "relaxed" in the sense that it almost felt like the music was slower...in the sense that it gave itself time. The music breathed much more. Rega felt like a punk get up and go table and Gyro felt like it was chilling and giving less of that forward motion, but in turn gave much more texture, microdynamics and nuance. These were the biggest differences that you didn't really need to look out for - they punched you in the face. For what I want and for me, it was Gyro all the way.
Recently I upgraded the Gyro with Truepoint (Pete's) suspension and it's a big upgrade. So keep that in mind if you go for Gyro - lots performance to be had from this and my comparison was without this upgrade amd without newer PSU (HR). Also, Gyro is very suitable for quite a few almost high-end tonearms. So there's that path as well.
I'd really like to hear a truly high-end rega like P8 or P10 in my system, as I know it's a completely different beast not only to my previous rega, but even to older RP9. Not because I'd buy one, but for reference.