MP3 ripped at a variable bit rate, using the LAME alt-presets. Not too big, sound good, will play everywhere.
Go to Tools/Options/Encoding
Select "MP3 Encoder VBR"
Select Quality = Custom
Click the Advanced button
Enter "--alt-preset standard" in the parameter box
Alternatively you can enter "--alt-preset extreme" or "--alt-preset insane"
Variable bit rate means that the encoder adjusts the bit rate according to the requirements of the music. This means that highly demanding passages are encoded at high bit rates, less demanding ones at lower bit rates, hence saving a lot of space.
The --alt-presets are basically a set of parameters for the MP3 encoder, selected after long testing to provide the best results. The differences between them are:
--alt-preset standard: imposes a minimum bitrate of 128kbps
--alt-preset extreme: imposes a minimum bitrate of 192kbps
--alt-present insane: in effect, 320kbps constant bit rate
I find that MP3s encoded using --alt-preset standard end up averaging 224kbps bitrate, sound better, and are not significantly larger than a 192kbps CBR MP3.
The difference between the standard & extreme presets appears to be the subject of religious war - files will be about 10% larger using extreme.