Navigation is all about the DATA. If it worked better (or worse) in a certain location, it is solely because they have access to quality data. Quality data costs a lot. Companies like NavTech used to literally drive cars down the road (think Google street view cards) and capturing everything (speed limit, number of lanes, boundaries, etc.) but they were bought by Nokia a long time ago. Not sure what is what these days. You can get pretty good data these days by leveraging free government data and things like OpenStreetMap. Routing is quite simple with good data. The harder part is conversion to narrative directions. How many times have you been given instructions to "continue to stay on XX for 500 feet" only to be told to "stay straight to continue on XX"? (Source: Worked for MapQuest for many years)