Just a little more fuel for the fire, CBR uses the same bitrate throughout the entire video, so some sections may come out over compressed while others waste unnecessary bytes encoding scenes that could have used less data to display the necessary visual info. CVBR is more consistent quality, using extra bits on more complex scene and using less to encoder simple scenes.
In short the same sized file will usually look better in CVBR. The major downside is encoding time. but since we're not encoding... it's not really a downside for us
Sometimes the size of CBR available for download is significantly large that every piece of it is higher quality. In these cases you may want to opt for the larger file if size is not a consideration. Byte for byte CVBR will give better quality overall.
