I've been using the Garmin 500 (mounted on K-Edge) for several years and have no desire to upgrade. I don't need touchscreen, color or smartphone connectivity. If these option appeal to you, then spend the extra for the 510. You can use turn by turn directions and the snail trail mapping feature with the 500. If you need something bigger with better mapping features, all the bells and whistles and have the cash to burn, then look at the 810.