Variable bit rate (VBR). Those you listed above are Constant Bit Rate (CBR). Arguably VBR is better because some parts of music don't need the extra bit rate to sound just as good. There is also Average Bit Rate (ABR). Have a look at Difference between CBR, VBR, and ABR? [Archive] - iAudiophile.net Forums and an even better explanation here LAME - Hydrogenaudio Knowledgebase (see under the Remarks section especially.) Where they argue VBR is best, then ABR, then CBR.