[theora] No quality advantage with two-pass?

[Remco]

The ffmpeg2theora chapter[1] of the Theora Cookbook says that the only
advantage of two-pass encoding is that you can hit a specific target
size. But isn't it so that you can reserve bits for difficult parts of
a video, which improves the perceived quality? It may be true that
Theora does quite alright without two passes, but it seems like a
no-brainer to me that two passes will always be better.

-- 
Remco

[1] http://en.flossmanuals.net/TheoraCookbook/FFMPEG2Theora