There's a seemingly-minor difference between the two that actually has a major effect, and makes Waze the hands-down superior app for vehicular navigation: the timing of the navigation direction call outs. Waze seems to have the timing dialed in to a perfect degree, whereas Google Maps leaves you either guessing if it meant this turn or that turn, or else unprepared to make a turn in the first place.
The differences between the two explain exactly why I use both...even though I don't like to.
I live in the freeway metropolis of Southern California and drive 40,000+ miles a year, using both Waze and Google Maps every day.
Waze is more accurate at my expected time of arrival. Maps will many times overestimate and then correct itself gradually while I'm driving. Sometimes there is a huge initial difference, as much as 20 min on a 100 min trip, even though both are using the same route. I guess this highlights the difference of using historical data more than crowdsourcing.
Waze can usually get me there slightly quicker. Anywhere from a couple of minutes to 10 min on a 100 min trip. If you are not in a hurry, it doesn't matter.
Maps has by far the better graphical interface. It's street names and exits are far easier to read at a glance than Waze. Maps also gives much much more information, in the form of pictographs and writing, on it's map. Maps also makes in far easier to see the "difference" between roads in the sense of where the go, and what type they are, such as freeway, highway, big or small roads.
Maps graphical interface also makes it far easier to figure out which exit to take and how it's going to look when you get to it. This makes it far less likely you will miss your exit or take the wrong lane. This is the aspect that makes me like Maps better than Waze.
Waze gives you fare more info about road conditions. Most of which don't matter as you are still going to take the same route anyway. You can turn all of these features on and off. It wasn't until a couple of years ago though that you couldn't turn off the feature of notifying you of a vehicle on the shoulder. This single thing made me stop using Waze in Southern California. Waze woud give "points", like it was a game, to users who reported things on the road (potholes, dead animals, pollice, vehicles on the shoulder and a host of others). But "vehicles on the shoulder" couldn't be turned off. In SoCal, there are always vehicles on the shoulder, so in a 100 min drive, I would be bothered by a pop up (that covered the map), about every 5 min. Super annoying. Now you can turn it off.
Maps for some reason, completley ignores the existence of certain toll roads such as the whole Fastrack system in SoCal. It won't give you the option of taking them.
Since Waze will suggest toll roads always if they are faster, which they always are, even if only by seconds, I'll initially compare the arrival time of Waze and Maps to decide it the time saved with Waze is worth the toll. Waze sort of has this feature built-in , but it's doesn't always seem to be accurate.
Waze is far, far slower at rerouting me if I make a wrong turn. So slow in fact, that in the city, it will frequently figure out how to reroute me and show me, after I've already passed the what it's suggesting.
So, my usual route choice is using Waze, primarily because it's slightly faster and notifies me of police on the side of the road.
If we could combine the graphics and rerouting of Maps, with the slightly quicker routes from Waze, we'd have the perfect app.