Oversampling is a technique to increase the sample rate of digital audio in an attempt to improve certain aspects of the signal, including antialiasing and noise.
To do this, the file is converted to a higher resolution (e.g. from 16-bit/44kHz to 24-bit/192kHz), converted to analog, and in the process one or more filters is used to correct for various issues inherent in the upsampling process.
This might make something sound better or not.
Oversampling has three big issues:
No new information about the recorded performance is added or created. Its chopping the original digital into lots more pieces only.
Upsampling creates imaging artifacts, frequency spectrum contraction, interpolation, aliasing and other issues. Various filters are used to help correct for these issues, but these affect the sound. Select a different filter, and the music sounds different.
The realism is compromised by these artifacts and other issues. Your ear is a magnificent instrument that can detect subtleties that affect the perception of realism. With the Aero DAC (and most R2R DACs), they have better realism, sound more "analog," and are less fatigue without using oversampling.