Navionics has excellent support. If you call them and have a specific area that you'd like to compare to your paper charts, they may take a screenshot and send it to you. I'm using Navionics S-57 charts from Chartworld of the Bahamas, and they seem pretty decent, although we're using our eyes quite extensively here too
Would you mind sharing their support phone number? Using email so far we were unable to get anyone to reply (with repeated attempts to different addresses).
Of course we are not an end customer, and we were looking for information on their modifications to S57 (to add support for Navionics-specific data to our product
). That said, they should, in theory, be interested to help - since this may potentially result in more sales of their charts.