Everything is very area dependant. If talking the USA waters, the free charts are excellent but is lacking good fishing bathy in some areas. The C-map bath areas (like East Coast and Bahamas) can be licenced for $100 list and are excellent. If you are leaving outside the USA then yes, you would most likely want the C-map option for whatever area. If they offer bathy in that same area, they will provide the bathy chart free when you purchase the Navigational mapping. I would recommend if you have an area of concern to open a support case with tech support and provide them the Lat/Lon and they can provide you some sample shots from the C-map Nav and Bathy in that area so you can see for yourself before purchasing.