The only "sonic reason" should be that one way sounds better than the other and that's up to you. Sometimes the differences are very subtle and it's hard to tell. Seeing as your pre is not a fully balanced unit, the signal would have to be converted to balanced, then when it gets to the amp, which is not balanced, it would have to be converted again. Seems to me the rca would stand the best chance of sounding better if there is no noise getting into them. If you don't hear an obvious difference, listen again for a little more soundstage, depth, holography etc, with the rca's. Good luck.
Pass Labs Aleph Question - balanced vs unbalanced?
I have a Pass Labs Aleph 5. I also have a Supratek Chardonnay Pre-Amp with balanced and unbalanced out. Do people think the Pass Amps sound better through balanced vs unbalanced? I understood that they were truly engineered to run balanced for best sound quality, but am not sure.
I am having a problem with balanced operation (that I don't want to mention here so I don't complicate my question), so I'm trying to see if its worth figuring the other problem out or just sticking with unbalanced.