A big reason for preferring +4 dBu as a reference, rather than -10 dBV, is because it usually implies that the +4 device can handle a larger voltage swing (across the board - inputs and outputs). Larger voltage swings mean that the signal can get higher above the noise floor, which translates into signals with more clarity and less low level "grunge."
According to http://www.sengpielaudio.com/calculator-db-volt.htm
+4 dBu = +1.78 dBV. The voltage difference between +4 dBu and -10 dBV nominal levels, then, is nearly 12 dB. I would be very happy to get 12 dB farther away from whatever noise floor I happen to have, when practicable.
In general (and assuming that you don't have a defective or shoddy piece of gear), more ability to handle voltage swing = better potential for handling audio. (Although, again, this is assuming that all other quality factors are equal. There are some "consumer" audio products which can probably beat the pants off of some "pro" products.)