i've used both, not the newest released one's, but the one's from like last year or whatever
ipod you get the cool lil touch glide thing, but the screen is smaller and not customizable
zune the screen is way bigger, you can customize the background with any photo (which is bad ***), the interface is easier to use IMO, i like the push button against the tocuh glide, and it has lots of other cool lil gimics and tricks to it
haveing used both, IMO zune hands down. I got a 30gig off criags list for $125 last year. best 125 spent ever.