Is there any advantage (other than convenience) at having the XLR output if there is no balanced input?
Nope.
Neither is there on most amps (speaker or headphone) that have balanced inputs as well. (Best example is the Rotel RB-1590 which I have heard in balanced and unbalanced mode compared to my Marantz PM-11 with the same speakers.) The Rotel is far from balanced, it doesn't even have discrete separate channels. The Rotel has a lot more power and control but the Marantz simply sounds a lot more smooth and musical, just right.
What is more, and I will get my butt kicked by some members for that, even a true balanced headphone system from source to end doesn't make any difference FOR ME.
I simply don't hear it with headphones and haven't had the chance to try it with speakers yet.
TO ME, balanced is a gimmick for audiophiles. It's only use is professional to run longer cable lengths which audiophiles don't use anyway as they try to keep their cables as short as possible, preferably half a meter or if not possible one meter.
I do use balanced though since my DAC, like most, has only two outputs: XLR and RCA. I use XLR for my main speaker system since the amp accepts it and RCA for my headphone and vintage amps since it's the only thing they accept. I switch my RCA cables from the DAC straight to the amp I wanna use at that time. No switch boxes in the chain, I don't mind putting a pair of cables in just before I start listening.
So, IMO, you should stop thinking about balanced or not and certainly frown upon opinions who tell you there's a difference between single plug 4-pin balanced vs. two plugs 3-pin balanced.
Have I written IMO enough?
So yes, the balanced output is simply there for convenience.
