FWIW stay away from Lowrance !
Why? I've got the 600C and it's ok for what I want. If you want the full Garmin experience then pay the money & get one, but as a simple device the Lowrance does what it says on the tin.
I admit the map availabilty is poor if you want more detail on the screen (a la Garmin) but I have the map on my knee & only use the GPS for waypoints.