There is also more resolution and inclusiveness of water features. There are a few other data fields and processes that can be done with greater accuracy using the 24K maps. Since I dont need it for the whole US but only for a part of the West, I got Topo 24 K.
My reason for buying Topo 24k West was that I wanted to have auto routing, which the free maps dont do. The free maps are great and will serve you well for geocaching.
The "Vertical Distance to Destination" data field in the trip computer also uses the DEM to obtain the elevation of your destination. I own the Topo 24k West DVD and bought after using free maps from GPSFile Depot. The DEM is used in this calculation and the 24K elevation prediction will be better resolution. TOPO US 24k on micro SD card with adapter - GPS Navigation - The highest level of topographic detail available for. For example many modern Garmin units allow you to see the terrain profile of the route ahead of you. Garmin TOPO US 24K Southwest - microSD/SD Provides detailed digital topographic maps, comparable to 1:24,000 scale USGS maps Contains detailed hydrographic. Contains detailed hydrographic features, including, coastlines, lake and. Not only does it give you better terrain shading but there are a few bits of data that are calculated using those DEMs and the higher the resolution the more accurate that data will be. Provides detailed digital topographic maps, comparable to 1:24,000 scale USGS maps. The 24K has a higher resolution Digital Elevation Model (DEM) that generates the terrain shading. The 24K gives you the ability to search for street addresses and street route to your destination. There are a number of advantages other than the resolution of topo lines to consider.
I've used both 100K and 24K and I much prefer the 24K.