First Foray into XLR

I always did and still do, only to a point, believe that the main reason to choose XLRs over RCAs is to reduce noise, when long cable runs are necessary.
Recently, while doing some A/B comparisons, with a friend, between a PrimaLuna, Dialogue, Premium HP, tubed power amp and a VAC, Phi-200, tubed power amp, I had a mind changing experience. We intensely listened and compared both amps through a pr. of Wilson Audio, Sophia-II speakers. We listened to the PrimaLuna, using the EL-34 tubes and the KT-88 and KT120 tubes. While the EL-34s sounded smooth and warm, the PrimaLuma needed the KT-88s or KT120s to come close to the overall, dynamics, power and presentation of the VAC. While the PrimaLuna, sounded very nice, indeed, it was not quite on par, in terms of dynamics, detail and overall scope of the stage, with the much more expensive VAC. Then we decided to run the VAC through it’s XLR, balanced circuit. I thought nothing could be better than what we had already heard, but WOW! Switching the VAC to XLR was mind blowing. We switched back and forth several times, ea. time concurring what we heard.
As mentioned by others - running XLRs, if your amp’s XLR posts simply tie into the RCA circuit and the amp doesn’t have a dedicated, fully balanced circuit - will net no gain. I’m now convinced, however, that with a very good amp, having a true, fully balanced circuit - I would choose the XLRs...IMO...Jim

@ieales We did not simply do A/B switching (I am not a fan of simple A/B switching). We extensively listened to both amps and to the VAC in both RCA and XLR inputs, at various volumes, and assorted genres of music, experimenting with two different, quality RCA ICs - a .5m pair of CablePlex Silvers and a 1m set of low capt. high res 99.9% copper. The result (even when compensating for volume) was consistently, a wider, deeper stage, with more air around individual vocals and instruments, when the Vac was running through it’s balanced circuit.
With your logic, nothing is, or sounds, any different than anything else - it’s just a matter of volume.
Even when adjusting for volume, we did not expect to hear an improvement on the VAC’s already incredible performance, but we did...Jim

@ieales
Looking back, I've got to laugh a bit at my own statement, as mind blowing and blows away aren't terms I usually use when describing, what are usually quite subtle differences, when comparing A and B, very nice components. I would not say that the difference was mind blowing, just the fact that it could possibly sound any better than it already did, along with the overall engagement of the performance.
As far as the driving device - not really sure which of John's collection of players and DACs he was using, certainly one far and above anything I have. Our original quest was to compare the The PrimaLuna to the Vac. We did not switch around any components - other than the two amps and cables, along with a bit of tub rolling with the PrimaLuna.
All of my equipment is single ended and in all, have been quite happy with what I have, including my silver RCAs...Jim