Single ended vs. XLR Connection Advise Needed

If your equipment have both outs/ins XLR and RCA more-likely it's not balanced. The true-balanced equipment has only balanced outs and that where it makse the point and sence. There has to be an output transformer present that separates positive and negative signals onto different signal wires. If you open up the cover you will realize whether the equipment balanced or not.
I always prefere the equipment that has either one of... instead of having both.

I've got to admit that Bear spells things the right way.
Having two sets of output circuitry is rather irrational for high fidelity reproduction since

a)they both have a common ground

b)the air acts in this case like a load too and there certainly will be a loss; sometimes the switch is designed to use only one output (something like output-selector) and the last

c)is actual resonant impact of one part to another in terms of transfering microphonics and induced noise from other components(especially if RCA are used and XLR is unused).

So the real truth is that if the component DOES have the true balanced output and RCA together, than you'd better of with XLR.

Also in true balanced connection the per/unit resistance is halved compared to the same RCA. Now that brings something more than noise immunity.