The problems you can get into with oddball sampling rates or other strange characteristics can far outweigh the benefits – particularly since you’re not starting with a live voice.
48000 is the video rate for television. 44100 is the sample rate for Music CD.
http://manual.audacityteam.org/man/Tutorial_-_Copying_tapes,_LPs_or_minidiscs_to_CD
If you’re making an MP3, your choices are much more critical than worrying about the quality of the high tones that only dogs can hear. MP3 crappy happens early and quickly. 32 is the absolute minimum MP3 quality setting for a mono show. 64 is the minimum for a stereo show. Any lower than those two and everybody can hear compression problems, gargling, bubbling and honking. Audacity defaults to 128 as does iTunes. Very good is anything above that. 320 is widely considered largely error-free, although the errors never go to zero.
As a comparison, I have an uncompressed stereo WAV file with a data rate of 1400. WAV is the format you need for archive of your work. You can always go down from WAV to everything else. You cannot come back up from low MP3 quality and it’s very difficult to edit MP3.
Koz