I am currently looking at the Montana 650T. Hand held GPS units are new to me. I want to use this for hunting, making trails on my property so I can make them from one point to another. I have heard some discussion about the 100k topo map that is pre loaded vrs. the 24k maps you can get free or from Garmin. What is the difference between the 100k and 24k. Is one better than the other. I am new to this. Thanks Steve