I also have both in my Humingbird 997csi. The detail is a little better in LBDN with the Navionics. Lakemaster is a bit better to the south and on BBDN. If you are not getting the 998 or 1198, plan on VERY SLOW screen refreshing with the Lakemaster chip. ( lots of info )
Lakemaster offers the target depth highlighting in Green and dangerous water in Red. (AWESOME FEATURE!) Also the water level offset is very handy. Ahh heck get em both !
I'm glad it did.