Get the Lakemaster, was up to Rainy for my first time in July. I ran the Lakemaster on my HB997 at the wheel, and my navionics on the bow in my HB788. I could not beleive the difference between the Lakemaster and Navionics. Most of the time I would spin my 997 around on the ram so I could see the map from the front of the boat. Lakemaster was tons better with detail.
Just got the Lakemaster Wisconsin chip, for most lakes that I fish the Navionics is fairly similar so far. Headed out to Green Bay in a few weeks and will see the difference there.