Hey guys, the best advice I can give is to look at each and pick which is best for your area or the lakes you fish. Nothing beats doing a side by side comparison before spending money. I cant speak for LakeMaster, but I can def help you out with Navionics info if needed. You can also download the Navionics app for any smartphone(still free I believe) to view any areas you like while on the go, this is great for lakes you plan to visit. I know right now with the Sonar Charts program(user recordings turned in) Navionics is processing over 20,000 recordings per week improving the mapping all over the US. You can also check out the Navionics WebAPP free of charge at Navionics.com. While using the WebAPP, once you zoom in be sure to toggle the button in the bottom left to turn on the SonarCharts layer to see the latest, updated mapping available for Navionics. IF you have any questions just let me know, glad to help!!
Here is a link to the WebAPP:http://webapp.navionics.com/?lang=en