Had both, CJ. The Garmin was good, came with a very good base map. It was further enhanced with autoguidance, 3D view (GPS and fishfinder mode) when using the sd card from Garmin. However, the detail in the fishfinder was average if not adequate.

The Lowrance Elite5 is very similar to the HDS5 which I presently have in my Douglass Craft. The base map is very basic, only enhanced when you use the Navionics sd card. However, the impressive part of the unit is the fishfinder, which using the broadband system gives unparallelled graphics of under the boat. Don't presently know what is going on, but I have had to send mine off to Navico due to a fault that has progressively got worsse in the last few months that has now resulted in a blank screen.

Hope this helps somewhat.