Many variables here. If the component is not "truly" balanced, the XLR capabilities are sometimes realized in a compromised fashion (I am told), which could yield inferior sound. In my system, balanced between some components is louder. When overall system gain is higher, perceived sonics can change due to how you have to set your pre-amp, etc.
RCA vs XLR
I was told by a dealer that RCA connections will tend to sound more 3 dimensional that XLR. Currently I am running everything balanced. Does anyone have an opinion and have you experimented with both formats?