dithering -- better in X1 or Ozone?

You should be able to export a silent track with dither and then import it (or bounce it with dither.
 
Then normalize and view the shaped dither with a spectral analyzer. This should show the shape of the dither. Different dithers shape differently. They should all have a similar amount of randomized noise, but the spectrums where the noise concentrates differs.
 
Give it a try...
find the one you like best.
 
This is an image of Power3
 

 
Keep in mind that dither just gets you a few more DB of useable headroom. For most high quality 24 bit digital recordings it is more of a best practice than something one can hear.
 
You can do the same to see the noise added by the tape sim for example. it has a bump at 60 hZ.
 
I think the console emulators depend on the sound being fed through them. Discovering what these add is a bit more complicated, but you take one track and copy it, flip the polarity (phase) and then bounce the two together, where only one has the Console Emulator to get an idea of what they are adding.