WMV has a better Quality/File-size ratio than MPEG.
But if your video is already in MPEG format, converting
it to WMV will reduce the quality somewhat. Every time
you re-encode the video using a lossy compression algorithm,
the quality suffers.
Movie maker.
Save the movie from the timeline and choose whichever wmv format is suitable
for the job in hand.
For best quality though, I'd remain with dv-avi.