XLR or RCA?

For long runs, rule of thumb being 50 feet, XLR will pick up less interference (less noisy), but in general there will be no real (measurable), as opposed to perceived, (subjective) difference. XLR is used by pros as it is can be used in long runs and is more reliable physically.

XLR balanced low impedence cable signals can run 100s of feet with ZERO noise.

Jmcgrogan2: please direct message me your address, and I will send you a sweet record.

My experience has been that if the equipment is fully differential, properly implemented, an XLR cable is a real bonus as the cable is sonically transparent. I've run some very good RCA cables, and in one application where the output of the source and input were fully differential, I could find no meaningful difference between a set of Mogami cables and anything of any price upwards of $1K. And I set that limit of $1K not because I think cables above that can beat the Mogami, it's that I just have no interest in spending more on cables.

And as noted, just because there's an XLR output doesn't mean it's better. I have a Pass Aleph Ono phono stage and I asked the kind folks at Pass which I should use into my Pass INT-150. The answer was- use the RCA

XLR any day for me. In my system, when used between my preamp and mono amps, it eliminates hum which is ever present when i use RCA cables.

Yes, you are right, full benefit is obtained if the system entirely is wired using XLR