The most obvious difference between them is the ability of the emap to accept Mapsource maps (with added memory chip) It's biggest drawback where you will be concerned is it's lack of watertight integrity. This could be an issue in the out of doors, unless you protect it well. Also, because it is not waterproof, I would think dust could be a serious concern. I like them both, but don't consider them to be equitable units. They were really designed with different purposes in mind.