I have a 2012 vintage Lowrance Elite4 DSI fish finder/chart plotter, and can select various parameters to display. My normal combination is Depth, GPS (ground) speed, battery voltage, water temperature and time (I think). I have four individual background displays, and can split the screen to show any two.
One is overhead zoomable chart, showing vessel's heading with an arrowhead, plus course to date. There is a compass showing course being taken. There is a fish finder, with many many different viewing options (depth scale, colour etc). Can't remember the fourth screen

You can store something like 400 waypoints, and can add one by moving the cursor to a point on the chart and saving it as a waypoint.
You have 10 levels of brightness as well as different colour schemes for the plotter screen as well (eg night etc)
I could go on, but really the extra expense is so little compared to a hand-held GPS that I tend to think the latter are really designed for hikers etc rather than waterborne users. I do agree that the USB card slot is vulnerable, and cover mine with duct tape rather than rely on the rubber flap.
Hope this helps. I called my unit "vintage" because since I bought mine, the newer technology has blown it away.....I believe the new Garmin units offer similar functionality.