Depends on use.
If for touring abroad, then Garmin xt2.
Why not a Chiggee thing or similar? Because it is basically using your phone. When the battery is flat/phone is too hot/you have no data/google maps not working/dropped your phone/phone will not charge because it detects water in charging port (this happens..) etc etc , at that point you will wish you had a bespoke sat nav ‘unit’.
I have my phone on a Quadlock too, personal choice, as I do long days and big distances when away. My phone also has TomtomGo app. …but see above!