I have always used Navionics map cards to help me locate certain contours, points etc while on the lake or prefishing for a tournament. I found on several lakes the Navionics card to be lacking in detail or it was inaccurate.
When I purchased my Lowrance HDS units I found a much better mapping system with more detail and other great goodies like vegetation and hardness of the bottom. The cool thing about it is you can create the insight genesis map with your lowrance unit while fishing or just taking a drive on the lake. It's simple to do.
With it I have found areas on my lakes in North Idaho and Washington that I never knew were there. Or I created a map where there wasn't one. See the images below of what the Navionics card had available for this lake and then the maps I created in less 30 minutes with so much detail I don't only see the 1' contours but also every depression, humps, points and ledges including the hardness of the bottom in the one picture. Information I need to locate the smallmouth I am trying to catch.
This is a game changer.