I usually use Waze, when I don't have the sat nav with me. I prefer wake for the real time updates based on other wave users indicating traffic issues etc. Saying that though, Google maps has integrated a lot of the features from waze, so I would say they are both about the same in functionality and it comes down to what you prefer.
I've had Waze since it launched but only started using it last year (I prefer GMaps' UI) and can honestly say it works a lot better than GMaps in avoiding traffic. I don't know why Google doesn't just implement all of Waze's features into GMaps. I'd prefer one unified app.
I like Waze because I use android CarPlay and in NZ gmaps doesn’t show the speed limits, and Waze does. I also prefer the font size as I can see the street names easily on Waze, whereas I struggle with them on gmaps.