Hi,
I have a 998c which runs the same new operating system as the 898c (new processor/coprocessor and Linux operating system). I have the Lakemaster MN and Navionics Platinum North in my unit. I HAD a Lakemaster WI, but returned it after some initial testing. What I saw with the WI chip was (bear with me) that the map orientation (with map orientation setting true North (Note: that's the only setting that will work - Humminbird software bug (see website))) that the map was shifted slightly to the west. Another way to look at is that (for example) a true north/south road would (displayed from chip data) would not line up with a Latitude/Longitude grid created by the unit. We tried Lakemaster WI chips in several unit at the dealer and they all worked the same. Does that make sense?
My advice would be to get the Navionics Platinum North only and call it a day.
FYI
Roger