While I do agree that Creative Zens seem to be much better then either option, im gonna say Zune.
I really hate iPods. They're over-priced MP3 players that have very outdated feature lists. I mean, no radio? no voice recording? even cheap, $70 players have those features. Honestly, they dont do anything revolutionary, they dont do anything different, and yet they cost just as much as players (such as the Creative Zen: Vision M and Zune) that have many more features then them. Also, a lot of peple complain that Zune's WiFi capabilities are limited, but in the end not many other players have that ability, so you have to give them some credit for doing something different.
In my opinion, iPods are a rip-off.