RCA or XLR?

Based on my extensive experience, I also prefer balanced XLR all the way.  However, in the end, as always, preferences are all subjective to each individual.  Happy listening.   

I have found the quality and synergy of the wire matters first. Then the which connection sounds best is component dependent. Not too long ago I upgraded to all ARC equipment. I had Transparent interconnects which are outstanding sounding, transparent interconnects. I started up decades ago, so I had all RCA. ARC recommends using XLR. So, I got an XLR and made comparisons... with the same wire and some others. My conclusion was that I could not hear a meaningful difference between the XLR and RCA (ARC is internally balanced , but they put a  lot of work into the conversion to non-balanced), but that the world has been migrating to balanced, both in component design and in interconnects so, I bought all new XLR. 

There was a large cost to this. Many high end XLR interconnects are much more expensive. In my case, if I could not have afforded the extra cost RCA would have been a great choice. 

But as noted above, you have to check. If you have high end equipment that is balanced... I'd simply go with XLR. 

I find moderately priced xlr cables to be as good as expensive rca’s. 

I prefer XLR for maintaining balanced connections and for the intrinsic reliability of the connectors.

All things being equal I prefer the design of XLR cables. The connectors seem like they will last forever. RCA always feels like each time I insert I am putting a tiny amount of wear and tear on it, which means there is a finite number of times I can do it before something bad happens. That number will probably last me decades but still.

However some designs actually sound better with one or the other connection type. Even if both are technically available on the components. So you really need to play around with your system and see if you have a preference for the sound either way. If they are equal I'd go XLR.