I agree with PanMan. However, with the Lowrance, you can have different .usr files on the sd card and upload your choice. With Humminbird, it is all or nothing with the upload from the SD.

Before I upload .usr files, I delete what is on the unit and upload what I select. This prevents waypoint mergers. Of course, I always save stuff before I delete anything. Habit. You can also name/rename your saved files with the Lowrance too.