1. Patents / licenses.
Yes, kids, it would cost us to include mp3pro decoder with Winamp. More info here
. mp3pro support will be probably never bundled with winamp; if you want to use mp3pro, you have to live with crappy third-party plugins. At least WMA can be used for free (it's based on microsoft's drivers).
2. Closed source, no publicly available libraries.
It's simple. You encode mp3pro or WMA under Windows, play them using Winamp, everything is fine. But if you decide to switch to another player, you might find that you can't play mp3pro anymore just because the mp3pro developers didn't decide to make a freely-available plugin for it, or creators of that player don't want to pay for licensing (hell, who does ?). WMA is less problematic here, at least most of windows-based software can handle it these days. But still, there are NO available mp3pro decoders for OS's different than Windows, WMA is currently available only for Windows and Mac. Decoders for other OS's might appear only if owners of these formats decide to make them (or someone pays them for permission, then releases commercial/shareware decoder); you can safely assume that WMA will be never ported to Linux for an example. If you decide to change OS or want to share your musc collection with a friend who doesn't use Windows, these formats might become totally useless.
3. DRM encryption in WMA.
Latest Windows Media Player encodes DRM-encrypted files which can be *only* played on the computer which encoded them. You can't give them to your friends; you might be unable to play them after reinstalling Windows on the same computer. Here
is an example.
Also take heed of this
latest drm security exploit vulnerability.
4. Converting to other formats.
Someday, you might want to convert your music files to WAV format for burning on CD. WMA format doesn't allow that. Winamp's WMA plugin used to do that a few versions ago, but it no longer does because of microsoft's licensing shit. (old plugin still available here
, use the diskwriter plugin as with any other format). Also, you need the old plugin too if you want to use DSP with WMA.
Both WMA and mp3pro are optimized for low bitrates. Of course, this makes novice users think that they sound better - "CD quality at 64kbps" according to official propaganda. Currently, Ogg Vorbis
outperforms both WMA and mp3pro at any bitrate. Modern MP3 encoders (LAME) totally outperform WMA at 128kbps and above; mp3pro format is low-bitrate-only so you can never get close to transparent quality with it (the mp3pro optimizations only try to restore high frequencies at very low bitrates, mp3pro doesn't have "high quality" modes). In other words - they *might* sound good to you now, but your audiophile friend will tell you that they're crap, and so will you when you get better speakers. For audiophile-friendly quality, use Ogg Vorbis with -q5 or better, LAME with alt presets or MPC. WMA/mp3pro might be useful for streaming, but current Ogg Vorbis version does almost everything they do, and does it better (and is FREE).
Ogg Vorbis - THE patent-free open format - http://www.vorbis.com/
MP3/LAME (free high-quality MP3 encoder) - http://www.mp3dev.org/
MPC (another high-quality format) - http://www.hydrogenaudio.org/show.php/showforum/11
for more info, dig HydrogenAudio forums
Addeneum: Why Converting Between Lossy Formats Sucks.
By encoding a track into some lossy format, you *always* lose quality. Therefore, if you convert from one lossy format to another (eg. from WMA to OGG), the destination file will always sound worse than source one, no matter what settings you use. If you want to get rid of your WMAs/mp3pros, re-rip source CDs into another format if you can; if the sources aren't available, it's better to keep them in existing format rather than convert to another one.