As with all software, one tends to stick to the allpication one knows
best.
I use Ozi partly because I don't want to be dependant on the supplier of
the
software for issuing expensive amendments, charging for upgrades etc.,
etc.


Partially true, Ozi "full" needs money.......


Chart Navigator Pro may well be far better than the basic Maptech
Navigator

Absolutelly. I remember about an old Offshore navigator version 5.something
that I didn't like much.... Chart Navigator Pro is redesigned from scratch,
and looks super to me, but it's my opinion... You can test it freely.......

Since I have many different charts in several different file formats, this
alone makes Ozi the king for me, but others may disagree.

What formats are you using? Basically I've noticed that BSB/S57 are most
common and maptech supports them both..... yes with Ozi you can go through
the raster/calibration method.