This fairly recent thread on the subject might of some help: https://forums.macrumors.com/threads/1698208/Tryin to decide which is better
Well, I'm biased against Google, so that settles it for me.
The stock iOS Maps app is really pretty good, in and of itself. My biggest gripe is that I would like a more easy to see set of traffic issue visuals.
The real issue is the mapping data - Google's is better, but it comes down to your needs. In my area, I've never found Apple's maps to be insufficient, but YMMV.