Video-to-.mp3 would mean that you’re only extracting/converting the audio portion of the video; .mp3 is an audio-only format.
That said, my experience has been good with using Apple QuickTime Pro; the encoders and choices of codecs range from .mp3, MPEG-4, AAC, H.264, even FLV etc., and H.264 renders the cleanest output IMO…worth the $29 price of admission.