The guide we were with on Guntersville a couple of months ago said that he preferred the LakeMaster maps because they were more detailed. And Guntersville is what I'm mainly interested in as we make 4 or 5 trips each year. I believe that he was using Humminbird.
I'd say someone who guides for a living probably knows best. I pesonally bought the Navionics for my use on G-ville when I was there and was very pleased, but I haven't seen the Lakemaster for comparison.