There can also be a difference in audible sound quality, depending on the encoder.
For example, with the right settings using EAC and L.A.M.E together, I can usually make a 128kbps track sound better than my buddy's 192kbps and some 256kbps track of the same CD-ripped song, when he's using "other" common encoders... especially if the other encoders can't make sense of errors on an old/damaged CD, and just encode them the way they see them.
But, even with EAC/LAME, I still prefer higher than 192, even if it's variable bit rate (VBR) to save space.