Hi Paulo,
I have used both mounts for many years and I know them well. The JP-Z is heavier but better built, more precise with tight tolerances in the entire construction, much more rigid and better suited for astrophotography than the G11.
The NJP JP-Z is comparable with the AP900 or a hypothetical G15+
Kind regards
Panagiotis
--
http://blog.astrodigital.net/