All things being equal (hypothetical) which do you prefer, XLR or RCA?

Not so hypothetical as some companies offer both rca and xlr connections on single ended only equipment for purely convenience sake. In these situations, I prefer xlr for their more secure connection and strain relief.

Over the past year, I've had a couple of opportunities to compare RCA vs XLR interconnects of the same brand/model, length (1 meter). The XLR's definately sound better in my system. More open, solid image, detail. Connected between a Marantz SA-10 and PM-10. Maybe those particular components were designed to be best with XLRs.

Thanks for the responses! @testpilot and @ron_hartman these are EXACTLY the kind of responses I was hoping for - thanks Folks!

The AES48 stadnard is what you should look up. Atmasphere has stated a few times on this forum that many manufacturers do not implement this spec properly. That is a main reason why various cables sound different and also why XLR and RCA also do not have much difference on those units.

My gear does support the AES48 standard and using anything but XLR is a waste of my money. Actually on my Benchmark gear I have to use XLR on the amp.

I run long XLR cables between my preamp and DAC and have the benefit of moving the rack far away from the speakers. I would not try that with RCA cables.

I have used single ended for the last fifty years. I have monitored reviews and forums on the subject... and specifically reviews on my Audio Reseach Reference gear... Phonostage, preamp, DAC, and amp RE160s. ARC equipment is balanced internally, and XLR is recommended. Most reviews notice a slightly better sound to the XLR. There has been a slow shift to XLR being noted as better across the industry. While not night and day... pretty consistently. XLR provides a louder signal, making it hard to compare with RCA. I spent hundreds of hours comparing different interconnects in the 80’s and 90’s... so I can read reviews and understand what they are saying and put it in context. I have a really good system, and am not going to waste time doing any more comparisons (especially since break-in is important and long for interconnects) So, I have been slowly swapping out my single ended for XLR... they are $4K per pop, I have one left. If I was starting today I would go XLR.

Also, as noted above it is recommended for long runs. I also have my equipment off to the side. Locating the equipment off to the side probably has a bigger impact than RCA vs XLR in short lengths, But they are all additive, so every little positive thing adds up. If you want a truly great system you want to optimize all the small stuff as well as big stuff.