It depends on your needs. What do you want? Hardware compatibility - or only PC playback? Do you want to archive your CD collection without any quality loss, do you want near to perfect quality with reasonable size or do you want files as small as possible with acceptable quality e.g. for listening while working on PC speakers? The only situation where wma(9) is (one of the) best I can think of is to use it on a hadware player with small memory (that accepts this format of course) so you're forced to use bitrates arround 80kbps.
WMA is strogly challenged by OGG Vorbis and AAC in low bitrate. Rumours are that AAC+ is very good in this, but we must wait and see. If high fidelty is desired, the WMA is outperformed by many codecs (MusePack, AAC,LAME VBR, OGG Vorbis..)
Compression? Yes WMA compression is better than MP3. But I say, just stick with MP3! Unless they start comming out with stuff that only plays WMA, and not MP3, dont go there. Plus, so you save 20MB over ur whole collection if u convert all MP3 2 WMA... later u'll want 2 burn with Nero, and u need WMA plugin... [sure u can get it free by piracy, and so do i, but its not allowed in this forum so, forget what i said] And to tell you the truth, i dont hear much difference between WMA's Lossless compression [@ 700 kbps] and MP3's 320kbps VBR. Sometimes i dont hear difference between 256 and 320, so whatever.
MP3Pro is only for low bitrates, which means low audio quality. Pretty useless piece of work. I beleive that OGG Vorbis is a good choice if one wishes to go below 160kbps. Based on what I've been told, the upcoming AAC+ should be sweet.
