rca vs xlr interconnect

If both units are true balanced designs, go with balanced lines and they don't have to be expensive ones either, save the bucks for better RCA wires, you can make some nice DIY balanced wires using canare or mogami wire and Neutrik connectors that will rival the big buck brands.

Ralph Karsten from AtmaSphere is correct.
You don't need expensive aftermarket balanced wires , good balanced circuits and decent cables are all you need.

Running single ended is another story, and this is where you shouldn't settle for less.

First post says it all.

If truly balanced.... go balanced connections. If not... save some dough and go RCA.

I used a fully balanced amp both ways... XLR and SE, my difficulty in clearly backing one over the other was this... one preamp was markedly superior to the other... the SE preamp being the top dog in that hunt. Using the non balanced pre with the balanced amp, the sound was stunning! Far superior to the previous and same brand as the amp, balanced preamp. Both were BAT. The SE preamp, I still have is Thor MK II. Sonically, the Thor is one of those preamps you always find a reason to keep around no matter what other things come & go... well, until I hit the lottery it'll stick around... it's that good.

Of course the BAT vk5i ran about $5K less or so than the Thor preamp at $10K. Maybe that's why the RCA pre outpreformed the BAT XLR pre.

So topology is one thing. Performance levels of the connected gear is another. One can't always say one direction is better than some other... there's just too many variables.

ordinarily the saving grace for XLR is it's quieter as a rule, than is RCA... and especially if tubes are involved.

Ordinarily. Results will vary.

You should try it both ways. Some people like the sound of balanced equipment connected single ended

With truly balanced gear and all other things being equal; XLR's are better.