I've yet to come across something where 'Triangular' hasn't been sufficient for me but I'm thinking now I might re-visit Pow-R 1.

 
Ditto.  I've always stuck with Triangle since it seems to work just fine and because it is the default.   But now I'm curious...
 
 
Edit: Jim, have you ever had reason to try different reverbs for this test?   Just wondering whether the quality of the reverb itself or it's frequency range would have any effect since it is the "source" being used by the dither process.
 

Thanks, Jonesey.   That'll save me time from trying to find an impulse response for Perfect Space that I do not have. 
 

A couple more questions about dithering ....

1. Do you dither when bouncing tracks within a given project?

I use Triangular dither when bouncing to tracks within a project.  I do a lot of bouncing in order to combine composite tracks, or to simply reduce the number of tracks.  My experience has been that you have to dither or the bounced tracks will have audible distortion.

2. For those who have tested different dithers, aside from the listening test, have you also tried to visually compare the waveforms? 

If you hear a difference, you should also be able to see that difference in the waveform (high zoom), comparing it to the original waveform. This could be a 2nd way to prove which dither is best ... kind of like getting a 2nd opinion.

Thanks