My advice would be to look at mapping available from each company for the areas you fish before making a purchase. Here is the Free Navionics Webapp:http://webapp.navionics.com
I can't speak for LakeMaster, but it he Webapp above is an awesome tool for checking out the mapping available from Navionics, be sure to toggle the button in the bottom left while zooming in to activate the Sonar Charts layer. If you have any other questions feel free to ask away!!