On the question of acccuracy, unfortunately it can only be determined by being there so you should only accept the views of users who have been there and used the charts
extensively. As an example I have been corresponding with Navionics
over the past month about geo-referencing errors in their Bahamas charts
. They now tell me they have "updated" the chip (covers Charleston to Turks & Caicos) but cannot or will not tell me if the errors I listed have been corrected. The only way I'll ever know is to shell out a few hundred dollars and buy the latest chip. I'm reluctant to do this as I might end up with the same inaccurate charts.
On the question of placement I prefer the helm
. I thought it would be a bit of a problem for trip planning as the Raymarine
C80 I have will not take a repeater but it has not turned out that way. Wherever you place it, remember that you will often be playing with the buttons and knobs, changing scales, getting info etc., so it has to be placed conveniently.
Good luck on your voyage.