RCA vs. Balanced - Sonic Difference?

Balanced offers much better noise floor - resulting in better dynamics.

It will all depend on the distance between the pre and the amp. Over the typical 1 meter cable there will be no sonic difference. Balanced cables reduce the ability to pick up noise over long cable runs. I used both with a previous system and at 1m I was unable to distinguish any differences.... but if you are like me and sometimes want to feel better about your gear regardless of whether you hear a difference or not then by all means use the balanced outputs.

The concept behind balanced cables, two conductors each cary he same signal only one is inverted so if the same outside noise (RF,EMI) is picked up by the two conductors the noise cancels itself. This is a different system than single ended, both are systems and must be evaluated as such. Some eqipment is "balanced" design and works best with balanced cables.