Comparison article, HD100 vs. Z1
 

It's in French, so you may need to translate it.

http://www.repaire.net/site/tournage...YHD100_JVC.php

I ran it through Alta Vista's Babelfish tool and it looks like a pretty balanced report. Basic conclusion seems to be that the image quality is very similar, so if you're trying to pick between the cameras then go by which one has the features you need. As others have pointed out, since these are very different cameras in terms of design it should be fairly easy to figure out which one is better suited to your particular needs.
--------------------

"The HD 100 is the heart of a true system inspired of what is done in the top-of-the-range professional circle. To further go Z1 it will require additional investments which it is necessary to be ready to accept. It will be necessary to also agree to devote time and the drive necessary to him to its good handling for which is not familiarized with the use of this type of camera.

"Z1 is immediately more accessible. It will tolèrera better the hesitations or the lack of experience of an operator a little less aguerri because of easy ways and of automatisms which are clean for him. On the other hand it is less flexible would be this only by its fixed optics."