I’ve honestly run both. I can say that both have pro’s and cons but in my opinion the CMaps up here in MN at least (not sure of your location) is much better than the Navionics chips.
Some lakes are better in Navionics but I find myself using the CMaps more.
I like the depth shading in Cmaps more, the mapping for the most part on the lakes I fish are better as well.
One thing about the Navionics chips is the age of it. The older ones had 8gig chips which some of the newer features take up more space and I wasn’t able to update the old chips with new features. They would send me a new chip with a 16gig card which was nice.
Just my .02 cents