Uber nav may be improved now, but it used to be clueless in my market. It wouldn't show turns in time sometimes (a lag). It would suggest turns onto one way streets that weren't possible. I couldn't see where I was going in advance like I can on Google.
We have major freeway interchanges here. Uber nav would say "take 50 west" then when I got on the interchange it would show "50 east". At that point it would be unsafe to suddenly change lanes. I tried to pan out on the uber nav and it wouldn't let me.
Twice I asked uber to refund riders due to navigation on freeway errors. It's all good and well to refund people's money but how do you refund their valuable time? (this was before up front pricing) One time support didn't refund my rider.
Finally, the font size and boldness on the top left where it runs down how many miles til the next turn - I can't see it clearly and I can on Google.
If you're using uber nav and not having any problems with it, by all means use it.
Yes it takes 15-45 seconds for Google maps to load when I first hit nav. I have got in the habit of hitting it asap once I've established I have the right rider(s). It wasn't that long before, only the past few months, not sure why.
If it takes a while I tell the riders, "I'm just waiting for the GPS to load, which way should we start going?" At pick up, the uber pick up page does show the initial direction which is great. Often that's all I need.
I think, experiment and see what works for you on your phone in your market with your eyesight.