N90 is head heavier and slightly less stiff than the N90II. It's not that hard to use at all! I can switch between the N90, VTZF, and AT700! If you must compare the N90II to something, I'd say VT80 or the AT900P would be good contenders.
Which N90ii are you refer to ? There are N90ii and the N90ii S-type.
I managed to try N90ii owned by a friend and it came to my surprise that it was very heavy overall (not only the head), even heavier than my VTZF 3u... He said, it was the "Chinese National Team" version but there was nothing different in the design compared to the market standard version.