As I understand it, Lakemaster is owned by Humminbird (Johnson Outdoors) and has been since 2011 ... so one would think that a Lakemaster map chip would give the greater results in a HB unit. I do know that Lakemaster Digital GPS maps are ONLY compatible with HB products, but what I don't know is whether the Lakemaster maps are better/more detailed than your Navionics maps. I would only be guessing to say that it was. (my GPS capable unit is a Lowrance)
You can also contact Humminbird_Greg :
gwalters@johnsonoutdoors.com ... and maybe he can give you more help.
... pappy