I want to know the answer to the following question:
Using VBR instead of a constant bit rate encoding makes which part of encoding less predictable?
All the background I'm provided with is that "Average bitrate is VBR implemented as a compromise between the two: the bitrate is allowed to vary for more consistent quality, but is controlled to remain near an average value chosen by the user, for predictable file sizes.". Is that enough to answer the question?