I broke down and got both but if you have to chose one it all depends on what lakes you fish and what electronics you are using. I mainly fish Percy Priest and OH so I'm forced to use Navionics because those lakes aren't on lakemaster. But on the lakes that Lakemaster has if you use humminbird you can do a lot more things than you can with Navionics. With Humminbird, Minn Kota and Lakemaster linked together it is downright amazing what you can do, it will change the way you fish for sure. That being said Navionics is a great chart too, shows great detail and seems to always be right on with my GPS.