1pass VBR should be quite worse than 2pass, since in 2pass the first pass is done so that the encoder can determine how to best distribute the bits between the frames to achive both given bitrate and a good quality. In 1pass however the encoder has to sort of guess.

This results in scenes that get too many bits when they might not bee needed, and not enough bits when they would be needed (blocks and other artifacts will be visible).

Maybe I'll do some tests on the weekend, but I think 1pass VBR is worse than CRF as well.