(
https://www.presonus.com/news/articles/balanced-unbalanced) Some fully balanced devices(like my BAT VK-D5) will output twice the voltage with their balanced connection, and will also vary impedances, which may sound much different than their single-ended connection, depending on things like whether the device being fed’s input is truly differential, it’s impedance, etc. Here’s an article that notes some of the variables, in it’s measurements/comments: (
http://www.stereophile.com/content/balanced-audio-technology-vk-d5-cd-player-measurements#MxCpgkJ7CX...) Keep in mind, if both devices are fully differential, more voltage/headroom=louder=sounds better to the ear, and may actually measure better(freq response), in some cases.