Hi Bill!
The advantage the combo units have is the ability to record everything while your underway. For instance, I put in 8 gig chip, set the unit to record, as I left port. I used the unit throughout the day, watching the bottom, navigating to different waypoints (piece of cake to show navigation and bottom contour at the same time). BTW, my units came with a rough map of the Sea of Cortez. Obviously a chip would be better, but remember I was told (by the folks who create Navionics chips) there was no way to add your waypoints to the chip (edit the chip). So with that knowledge, I did not see the need for a chip.
Anyway at the end of the day, back at the condo I pulled the chip out of the unit, set the laptop up, and using fast forward I could see an instant replay of the bottom contour. The main advantage was I could stop the screen, move my cursor over any point of the screen and I instantly got the exact waypoints of that location! I was able to pick up new potential fishing locations that way... If you want, I'll send you a brief copy of a recording I made back in Feb. Likewise when I heading out to a known reef, and I pass an interesting "area", I can always review it later, whether I'm fishing or back at the condo/home... I do not know if one can correlate the same type of recording data when you have different units, gps and sonar. I do carry a spare GPS/sonar unit on the boat simply because I've got too much invested in the trip to rely on such a simple duplication. My backup unit (which cannot record data) was only several hundred dollars.
Last bit of info, I've taught GPS useage since 1997 for Hunter Education and I personally have been very disappointed with the product support given to me by Garmin. I have also found Garmin units (that I've used and demonstrated) take a very long time to acquire satellite signals, and will easily lose their signal when used in a heavy tree canopy. The lowrance units on the other hand acquired quickly, and never lost a signal, even when used in the basement of a third story house.
Last bit of Garmin experience, remember y2k? I called Garmin at the time, and they would sell you a patch which you could download to your unit, if you wanted to continue using your unit. I do not know if this was for all units, I only know it was for units that I had inquired about at that time. Lowrance/Eagle units were not affected and needed no patch.
Obviously one does not have to worry about heavy tree canopy on the ocean.
Just thought I would throw in my experience and opinion on this Ford /Chevy /Dodge debate.
Don :boat:
