Updated
With many YouTube videos, I see a choice of downloading the FLV or the MP4
versions, and I go with the MP4 versions. That would be preferable
than doing yet another conversion to WMV. I believe both FLV and MP4
versions are offered directly on these web sites.
The excellent freebie media player, "Media Player Classic", plays MP4 files,
too (in addition to WMV)!
I'd stick with the MP4 format (it is a bit better than converting again to
WMV), unless your sole media player is Windows Media Player. I figured
most people by now have the excellent freebie "Media Player Classic", a
*very* welcome addition - to solely having Windows Media Player.
Just as a footnote:
That said, the later versions of WMV (WMV3/9) are pretty close in
compressibility to MP4 (using the .H264 codec), but MP4 is a more universal
format - PLUS that format is readily obtainable using the DownloadHelper
plug-in.