How Do The Gps Capabilities Of New Mobile Phones Compare To The Gps Models By Garmin, Tomtom, Etc?

For example, compared to the Garmin Nuvi series, or something similar. Is it like comparing apples to oranges?
Can some phones be used as car navigation? How good are they at pedestrian navigation?
I’m considering buying a GPS, probably a Garmin Nuvi 750, but if my next cell phone might fulfill the same duties, maybe I won’t.
Thanks for any information or advice!