RCA vs XLR and Balanced vs Unbalanced

The primary determinant of which will sound better is how the equipment is designed (balanced or not… as MC and others have noted), The manufacturers might tell you which is better… but the reality is the difference… particularly if your equipment is <$2K per box is not likely to be big. I would guess, that it would be more cost effective to stick with single ended RCA) until your individual components cost more than $5K. Mine are closer to $20K each and my upgrading to XLR was not real noticeable although this is what the manufacturer recommends.

My Ayre stuff is fully balanced with both XLR and RCA's.   XLR wins easily.

i agree that ayre and arc stuff always seem sound noticeably better running balanced...

Thank you all for your input. I am getting a better idea of the what I need and do not need to consider in my decision making process. I am running a Musica Pristina A Cappella III  connected via I2S to Denafrips Pontus that is connected to W4S STI1000 V2 using XLRs to Cornwall IVs. In this set-up I also rotate in a Fisher 500C that is connected to Pontus with hybrid XLR-RCA cable. The components are located on a rack between the speakers that are approximately 8-9 feet apart.  I'd like to transition to a Decware mono set-up with a true balanced pre-amp (TBD/suggestions?) where I can locate the monos next to the speakers  and move the rack to a side wall.  Moving components to a side wall will necessitate a run of approximately 12' to for right channel mono and 18' to left channel mono.  That is why I am inquiring into balanced vs XLR and balanced vs unbalance.  Any suggestions for an preamp ($3K ballpark) that would work with this set-up or any other thoughts on this set-up are appreciated. 

As already answered above home distances are nowhere near long enough to justify XLR. I will go out on a limb right now and say all the info you will get on this will focus on technical jargon and totally miss the big picture. Which is, as also previously stated, quality matters in audio more than anything else. You can spend a fortune on high end components and then ruin it all by using long runs that cause you to cheap out on wire. Quality wire is so much more important than any technical considerations, but you can flail and flounder many years and never figure this out. It happens. I have seen it.

If you are forced by the layout of your living arrangements and traffic flow that is one thing. But if you are using long runs hoping to gain more in having things off to the side, forget it. Not happening. You will cheap out on wire, and this will cost you ten times what you hope to gain.

XLR vs RCA does not even factor into it.