It depends how you want to spend your money, if you want a good mp3, that can download all your music into another comput, really good memory for its price, but looks like anal discharge, then you go with the Zen.
If you want a mainstream cool kids, good looking, earphone breaking, waste of money, breaks easily, really easy using click-wheel, color screen, and has a bunch of gadgets to go with it, then you buy the iPod.
It depends on how much money you have, I had two iPods, both 20 gig black and white, and they served me really well, but lost both of them, now I'm getting a 60 gig iPod photo since my collection got bigger and it's sexy.... but if you go with the Zen, I wouldn't punch you.