The following answer talks about the Zune in comparison to the Ipod, but it still answers you question while talking about it in general. At the bottom it compares it to a Zune 80GB to an Ipod 80GB. See sources for more helpful answers/reviews.
*Note: All Zunes have the same firmware, so 4, 8, 30 and 80 are the same except for physical attributes. Also, I would recommend getting the 80GB IF you have the money. If not, the 30 is fine. But the 80GB is more updated and will most likely have far less problems. I am going to get it even though I don't have nearly 80GB of stuff.
Also, the Zune can NOT use iTunes to clarify from the answer above. They have to be converted. See compatible files at bottom. Anyway..
Go Zune for these 16 reasons;
1) The Zune has much better support ~ All the devices get the same updates, whether it be an 80GB, 30GB, 8 GB, or 4GB. Apple doesn't do this with their players.
2) The screen is far better ~ Comparing to the small screens of an Ipod to the large Zune screen. It's also not made of plastic or another cheap material.
3) Personalization ~ You can customize your Zune's background with YOUR OWN images (they look good because instead of trying to fit the whole image in, it takes only a part of it), a case you can get with the same color as the player, or even laser engravings on the back of the 4/8/80GB. Go here for engravings:
http://www.zuneoriginals.net
4) Scratch-Resistant! ~ The Zune just doesn't scratch on the body. You'd have to try to do that. Unlike the ipod where after a year all you see is scratches.
5) Better UI ~ The Ipod’s interface is pretty boring, where as the Zune has a nice feel to it, and navigating is quick and easy.
6) FM Radio ~ You can listen to the Local news, contests, new music, talk radio, whatever is on the radio. The Ipod doesn’t even have one.
7) Player Durability ~ My Zune has lasted me for a year now. Most ipod users get more than one a year.
8) Subscription service "option" ~ For one monthly fee, you can subscribe to an ‘all-you-can-eat music subscription at the Zune Marketplace.
9) Better integration with the Xbox 360 ~ The new Zune update will promise better integration with the Xbox 360.
10) Zune Software > iTunes ~ The Zune software is far more simple than iTunes, and you can try it free on their site ( Zune.net), under Products.
11) Better Included Headphones ~ The Zune’s included headphones aren't too bad. Compared to the Ipods which are horrible. Also the new 80GB Zune comes with Earbuds, which are also far better.
12) WiFi ~ You can share music, videos, and poscasts with other Zune devices.
13) WiFi Sync ~ you can sync to your computer without connecting it, meaning you could be downstairs (maybe) and sync upstairs.
14) Same price as iPods ~ Same price as regular iPods of the same specs, but includes more features. Now the prices may even be less.
15) Sync with Windows Media Center ~ sync recorded TV shows onto your Zune device
16) View in landscape mode ~ you can view pictures and videos wide screen.
In general, the Zune is a more balanced player seeing as it can play Pictures, Movies, and Music on one device. With the Ipod you have to get different devices that specialize in different areas (i.e. Ipod Video) to be good at it.
Comparing the two:
Audio files supported:
Ipod: AAC, Protected AAC, MP3, MP3 VBR, Audible 2, Audible 3, Audible 4, Apple Lossless, WAV, AIFF
Zune: AAC, MP3, WMA
Video files supported:
Ipod: MPEG-4
Zune: MP4, MPEG4, WMV
Image Files Supported:
Ipod: JPEG, BMP, GIF, TIFF, PSD, PNG
Zune: JPEG
Resolutions:
Ipod: 640 x 480
Zune: 320 x 240
Dimensions; Zune 80 Vs. Ipod 80
(W x D x H)
Zune: 2.4 in x 0.5 in x 4.3 in
Ipod: 2.4 in x 0.6 in x 4.1 in
* Zune height is larger because the screen is .7" larger.
Yes, it looks bad for the Zune. But the 16 reasons above outweigh this easily, in my opinion. Find more in the below links (click on specifications)