I just purchased the HDS 5 with U.S. basemap.......I doubt any other units are very similiar to these units. My last unit was the lms 332c and after a day on the water with the HDS 5, I'm a little disappointed. To me, the processing speed is much slower than my last unit. I just did the software update for the HDS units, but still it's slow in comparison. Also, my old lakemaster chip doesn't give me anything more really than the basemap. I suppose I'll get used to using the unit and would like to know if there's a way to turn off the transducer while the unit is still running???........I don't like fishing shallow water with the sonar on and when I want to put the boat up on plane, I have to wait at least a half minute for the unit to load back up if I have it turned off.