I don’t know… I’ve found that 10x zoom is generally enough. (Unless you are a paparazzi, and do a lot of long range shots from your tripod). For video of course the extra MP don’t matter… for stills the extra MP will somewhat offset the loss from using the digital zoom, but I don’t know how to calculate the point where they cancel each other out.
Interesting in this particular league table
http://www.camcorderinfo.com/ratings.php
the top 10 (and 15 of the top 16) all have 10x zooms.
The Optura 600 is the US model of the MVX4I (number 4 in the chart).
Mark