Do you want to store thousands of photos, music and videos on one hard disk media jukebox PMP or is a smaller, less capacious (and possibly more durable) solid state PMP more your style? You can increase the amount of music, photos or video you can fit per megabyte, by upping the compression ratio. The drawback of this is that it may involve time-consuming re-encoding and result in reduced quality.
Most of the bigger PMPs use mini hard disks that store 30GB-160GB or more of information and a handful may offer expansion via a flash memory card, however this is rare these days.
Interface features: photo, video and music functions
OK, so pretty much all PMPs can view photos, movies and play music but there are a wide range of playback software features and operating systems out there.
If you're a buying the PMP primarily for photo functions, then the ability to zoom, rotate photos and view them as thumbnails or slideshows may be more important to you. You may even want a PMP with a built-in basic still and video camera, such as those from Olympus or Archos.
Then there's video playback. Would you like to be able to bookmark parts of videos for easy resuming? Do you want subtitle support? Can the playback switch between widescreen and standard 4:9 aspect ratio? The importance of such features depends on how you plan to use the device.
With music, you should check how easy it is to make a playlist on the device itself; if album covers can be displayed during song playback; plus, if you can view lyrics and also browse easily through your files.
You won't know how intuitive a device feels until you actually try it yourself. Try to create a track playlist within the device (which isn't always possible) and check to see if there's smart (automatic) playlist creation. This might be based on songs you haven't listened to in a while, songs you've listened to a lot, or on certain music genres.
Pay really close attention to the interface -- you're going to be using it a lot, so you may as well choose a player with a navigation method you not only understand, but actually like as well.
Digital Rights Management (DRM)
If you download music from a music download service, DRM is something you should know about. Most Australian music download services use Microsoft's WMA format and use a standard license permitting a music file to be downloaded once and to copy it an unlimited number of times to up to two hardware music players that work with Windows Media Player 10. Microsoft's "Plays for sure" program: a Web site (www.playsforsure.com) and associated logo will help you to choose from a large selection of players that are guaranteed to support DRM WMA files. Not every player that supports WMA will be listed, so you might also want to double-check that the player you have your eye on has WMA playback.
NOTE: Because of its own DRM technologies and to encourage users to buy an iPod, any songs downloaded from Apple's iTunes Music Store only work with Apple's own iPod (and a few select products whose manufacturers have deals with Apple) -- this was the case at the time of writing, but make sure you check before you get locked in!