Pitch Shifter -vs- Stretch process

Is there any difference in the quality between these two?  I see that the parameters are about the same for each.  I have to shift a recording down a whole step to give out as a rehearsal reference.  Even though it's not for public release I'd like it to sound as good as possible with the tools on hand.  There are basically three components to the track: Lead vocal, guitar, and choir.  The choir and guitar don't sound too bad shifted but the vocal sounds pretty unnatural.  Any suggestions welcome.
JTC