If you're using a good MP3 encoder, then VBR is not specified as a percentage. (example: LAME)

Next, VBR will not be better than a very high bitrate CBR (256/320Kbit).

That said, VBR can be very good. Take a look at www.r3mix.net. There are other places to read. Check out this thread for a small discussion and pointers on what to search the net for (to get info on an updated LAME preset).

Bruno