This review is a delight:
http://www.maz-sound.com/mp3.html
Some special quotes:
(regarding mppenc - the guy doesn't know how to count)
"comes with 4 default presets: thumb (very low bitrate), radio (mid range bitrate), standard (very high quality, default), xtreme (even higher quality, for extraordinary hearings only) and insane (for those who prefer full frequency response"
(regarding Vorbis RC3)
"NEW: bitrate management, instead of choosing one of several VBR modes, you can specify average bitrate, put boundaries on the bitrates to emulate CBR (useful for streaming), or the default VBR modes which have millions of possible quality levels"
(regarding SCMPX - someone should tell him that it's based on Dist10)
"SCMPX and LAME are the reason why I removed all TOP symbols from the other MP3 encoders and even kicked some to black hole"
(regarding AudioCatalyst)
"the XING encoder is really faaaaast, the audio quality is OK considering the speed of the encoder"
Really worth a laugh.
Regards;
Roberto.