Garmin Data Cards
Whether you use the data cards or buy the CD, it will be exactly the same as far as the GPS itself is concerned. No difference. But if you buy the CD, and download the areas you want, you will have the charts on your laptop. Using the CD with the laptop gives you a lot more options. Route and trip planning can be done on the computer. You can do your route planning, mark waypoints, course, etc. and transfer that to the GPS. On the computer you can get distance, course, water depths and a lot more info. that is very useful in planning trips. I have found this to be extremely useful, as you can not only do route planning, but get total distances, and pretty well give yourself time frames too.