I've used both stand-alone Garmin, Tom-Tom, phone aps and (in my current car) integral sat-nav.
Phone apps are not for me and I don't see huge differences between Garmin and TT. The Mrs has a Garmin which was our choice after lots of research, it's updated OK and had no glitches.
For me they are all an aid to navigation so you do have to be on the lookout for the odd issue in routing.
My car integral has traffic on it and that is mostly brilliant but does sometimes warn of jams that aren't there.
My daughter is just learning to drive and if she passed her test tomorrow I'd buy her this for under £50...
Halfords | Garmin Nuvi 1300 Sat Nav - UK & ROI