There is little reason today to go with really low bitrates, and WMA is a completely proprietary format supported by a fraction of the devices that support MP3.
If you absolutely have to shoe-horn in small files in a small memory space then maybe WMA is the choice, but if you want the best sound and greatest compatibility, you should be ripping your CD's with Exact Audio Copy and encoding the MP3-files with Lame. Both programs are free and absolutely top notch.
See r3mix.net for lots of good info.
There are other formats that beat either of them, on paper at least, but obviously not as broadly supported as MP3.
Thanks everyone. Space and compatibility are not an issue. I'm currently doing 256 mp3s on a 40 gb drive in a computer connected to my main system. I use this as a jukebox for parties or working around the house. I just wanted to get the best possible quality out of the sound that I could.
That's pretty much what they say over at r3mix.net, vbr is the way to go. Based on the sound I myself get from VBR files, I would definitely agree; you save space but get great sound quality.
In fact, might even be better (albeit undetectably so, since 256 CBR is already virtually impossible for almost everybody to separate from the original - yes, I like qualifiers ) since VBR's can go up to 320kbit momentarily if the encoder decides the music being encoded requires it.