VBR will be always better than CBR if and only if your encoder use the latest LAME codec (3.92).
It has been tested at 128 kbps and up.
LAME VBR is very good because it can give 320 kbps to a frame and 32 kbps to another. Some encoders have problems with that.
A real VBR file, the little problem with it, you can't predict exactly which filesize you'll get. If you encode classical music, you may end with a smaller filesize than predicted. Very complicated music with alot of noise like metal could end with a bigger than expected filesize.
At least, you'll get very good sound quality, higher than the equivalent in CBR.
If it's another encoder, the problem I mentionned in my previous post could happen.
It's strongly advised to at least encode over 112 kbps in VBR with poor encoders.
Please use LAME, other encoders mostly sucks.
It will be better for your ears