I did have a Lowrance X97 on trolling motor and X97 on transom and was using a Garmin Map 76S as GPS mounted up on front of the boat.
I bought a Lowrance 522C igps and Navonics 2008 Hot Maps chip and put it on the trolling motor and continue to use the Garmin 76S to mark waypoints along with marking them on the 522C. It is my understanding that if I would ever need to reset the Lowrance I would be losing the waypoints on the Lowrance. I have the extra X97 in basement as a backup for either graph on my boat.
The Garmin is a backup for my waypoints. I use the Garmin to bring my waypoint into my computer into Easy GPS or FUGAWI maps.
Another handy thing about still using the handheld GPS using it while fishing with a friend using his Hummingbird sideview. After he has marked a waypoint on his side view he positions his boat over the waypoint until it shows up on his graph at which time I mark the waypoint in my Garmin hand held. At a later time when I get back on the water in my boat I find the waypoint using the Garmin handheld positioning my boat until the waypoingt shows on the Lowrance 522c graph at which time I punch in that waypoint on the 522c.
“There is no difference between communism and socialism, except in the means of achieving the same ultimate end: communism proposes to enslave men by force, socialism—by vote. It is merely the difference between murder and suicide.” Ayn Rand