I would take a look at all the lakes you fish and then see which chip has the best HD maps for those lakes.
I use both the LM and Nav chips and some of the LM chips like Rainy lake and LOW and Rainy river. Lm has some great chips but Nav also offers some helpful.
For me, 90% of the time, I have a LM chip in the units I run.
I also like th LM chips as they seem to zoom in and out much faster than the Nav chips.
Nav seems to be better with the trade in on the older chips to upgrade but one usually has no issues selling 1 year old chips to upgrade annually when they upgrade with more HD lakes.