Check this out over at Anandtech. The PC-Centric site is very favorable to Apple's market leader.

If you're looking at a device for playing audio, then look no further than the iPod Classic. Apple has had 6 product generations to refine the original iPod and it shows in every way. The battery life of the Classic is unmatched by anything else we've looked at, even the iPod Touch can't close to within 75% of the battery life of the Classic. Meanwhile the combination of the legendary click wheel and the iPod UI is effectively as close to perfection as anyone is going to get for usability; the wheel is sensitive enough to allow for minor adjustments while still allowing for anything to be done in one complete motion. Our only problem with the Classic are the earbuds: they're terrible, if you're buying a Classic make sure to buy some real earbuds to go with them.

The Zune has the UI and the audio fidelity it needs to be a winner, it just doesn't have much else. The battery life is just acceptable and could stand to be a lot more. The Zune pad is an interesting concept but when it screws up it's frustrating. The Zune marketplace's payment scheme is awful should you need to purchase something you can't get DRM-free. It's never a bad audio player if you stay away from the Zune Marketplace, but in either case the Classic clearly surpasses it.