I can answer that emphatically - use the unbalanced connection whenever you can, and in truth that should be always in any normal home situation. I use a 25' unbalanced run between my preamp and power amplifier closet, and if anything, my setup is more critical of noise than normal with my 106dB/watt efficient horn speakers.

Differential connections via XLR will always degrade the signal more than the simpler unbalanced route. The signal must be converted from the native unbalanced state inside your preamp to differential, which means extra circuitry which the signal must go through.

If you don't have a ground loop which cannot be dealt with by any other means other than using the differential connection, go with unbalanced.

The power amp will work just as well with either connection.