That is not a fair comparison, Porsche does not directly compete with chevy and ford except in the exoticar class(vette and gt). However to use your comparison, I'll take my (chevy)garmin etrex that is designed to be a little consistant workhorse over a(porsche)magellan that like the porsche, is a little particular and finicky.
However, I have to agree with JohnnyVegas, go with what ya' know baby. Its all in what you are used to.