Any signal at the input of one side of the amplifier will result in two outputs, equal but opposite of each other. Differential amplifiers present a constant load to the power supply, resulting in less noise in the power supply. Differential amplifiers have roughly 6 dB lower noise then the same circuit executed in a single-ended manner. This can be very important in moving-coil preamp sections. Differential amplifiers tend to cancel distortions that single-ended amplifiers cannot.
Drift is reduced by the tight coupling of the two halves of the amplifier.
Performance over time is improved. Common-mode rejection ratio is the measurement of a differential amplifier's ability to not amplify noise that is common to both inputs. It is typically at least 55 dB, and can approach 140 dB in some critically-tuned designs. Differential amplification takes more parts to execute. On the bench, in the textbook and in real life, differential amplification provides greater performance, particularly from DC to 100 KHz, the audio region.