The Nano ($149-$199) remains the more attractive of the two. Its new look is sort of growth-spurt chic, combining the long, lean looks of earlier models with a reoriented 2-inch screen that debuted with the shorter, wider third-generation model. In addition, its sides are rounded, which gives it an oval-esque shape that felt awkward cradled in my hand but was easy to slip into a back pocket.
The new Nano comes in an array of bright colors, and this alone may appeal to buyers who want something that stands out from the crowd.
The latest flash memory-based Zune ($150-$200) comes with some new color options, but they're not nearly as loud, and overall the device is identical to the one Microsoft rolled out in October. At 3.6 inches tall and one-third of an inch thick, it is the same height as the new Nano but noticeably bulkier.
Looks aside, the biggest differences are in the players' new features, which include wireless music downloads and streaming on the Zune and an accelerometer that makes it easier to manipulate song-shuffling, gaming and image viewing on the Nano.
Unlike the iPod family, Zunes have always included a wireless feature, but it was limited to sharing songs with other Zune users (who can be hard to find) and to synchronizing music, videos and photos with personal computers. On the most recent Zune, this has been expanded so that when users are in Wi-Fi hotspots they can access the Zune Marketplace online music store straight from the device.
The ability to download songs over the air is not unique - the Nano's big brother, the iPod Touch, can snag songs from Apple's iTunes Store via built-in Wi-Fi - but it certainly gives the smaller Zunes an edge over the wireless-less Nano, and a free update makes it work on older Zunes, too.
I found the Zune's Marketplace feature easy and definitely satisfying, especially since I tend to think of music I want while I'm listening to tunes.
The feature lets you search by lists of top songs, or by sluggishly tapping in artist names; most users will probably find the former simpler, but I did appreciate the option of the latter.
Another neat Wi-Fi feature on the Zune is the ability to download songs you hear over the built-in FM radio. This was simple, and only required a few clicks from start to finish. If you don't have Wi-Fi access, you can still choose songs and they will queue up so you can download them the next time you connect to your computer.
Users who pay $15 per month for Microsoft's all-you-can-eat Zune Pass music subscription can also stream songs over Wi-Fi, and I found songs came in pretty clearly.
The new Nano, meanwhile, does have a few tricks up its chrome sleeves. Apple added an accelerometer, which it had previously included in the iPod Touch and iPhone. The accelerometer lets you do things like turn the Nano sideways while listening to music to scroll through album covers. That had its own menu tab on the previous Nano. Or now you can give the Nano a shake to shuffle it to another song.
I thought the shaking-shuffle feature was kind of annoying. With the slipperiness of the Nano's curved sides I worried I would throw the little guy onto some subway tracks or a busy street while commuting.
But the accelerometer can make games cooler. Apple included a simple game called "Maze" to give users an idea of how this works, and I was surprised at the responsiveness of a little, silver on-screen ball as I tilted and maneuvered the Nano. This was one trick I wished the Zune could learn.
You can also view photos either in portrait or landscape mode on the Nano; the Zune only shows photos in landscape mode, and both devices limit video playback to landscape mode, too.
Another highlight of the Nano's makeover is the new "Genius" feature, which is meant to help you put playlists together by taking one song as a starting point and suggesting other tracks with a similar sound or feel. Or if you try this from a computer, while using the iTunes software, a Genius sidebar shows related songs you can buy from the online iTunes Store.
This gave me some interesting suggestions, like Fujiya & Miyagi's light electro-groove tune "Cassettesingle" when I used The Bird and the Bee's dreamy-sounding pop song "Because" as a starting point. But it seemed a bit off-base by suggesting Jason Mraz's cheerful "I'm Yours" when I started with Rihanna's dark-sounding "Disturbia."
The Zune's latest software includes a similar feature called Mixview that uses thumbnails of album art and artist photos to illustrate users' listening patterns and give music suggestions.
Visually, Mixview is miles above the Genius feature, as the images show up in a circular pattern around a rectangle containing a user's profile information.
I liked being able to click on each thumbnail to find related albums, artists who may have influenced the music I'm checking out, or profiles of other Zune users who listen to that music.
Beyond these features, there are plenty of similar specs on the two players. Both sound good, power up fully in about three hours and are rated for up to 24 hours of audio or four hours of video playback per charge.
Their screens appeared similarly bright, and a photo of my brother's bandana-clad dog looked equally crisp (and cute) on the Zune and Nano.
Videos looked very good on both, but the Nano is easier for watching because it has a larger viewing area - 2 inches on the diagonal, compared to 1.8 inches on the Zune.
Both are solid multimedia players, though. And while Apple may be at the front of the pack right now, clearly Microsoft is making strides - and maybe making consumers think twice before running out to buy a new iPod.