Google Maps much better
I used my iPhone as my GPS on 2 different motorcycle trips originating from Austin, Texas this last Summer. I used both Apple and Google maps and really wanted Apple to be the winner because it's just easier as the default map app.
The first Southwest trip was for about 5 weeks and went from Texas through, New Mexico, Utah, Arizona, Nevada, and back to Texas. The second trip was also about 5 weeks and went through the mid-west from Texas through Arkansas, Missouri, Kentucky, Tennessee, North Carolina, Virginia and Louisiana... back to Texas.
The Apple map results were consistently horrible, inaccurate, and got me lost several times. The Google maps were always perfect without exception.
Haven't tried since iOS7, but I find myself not even using Apple maps for quick local directions. I cut/paste addresses from the default Apple map results right into Google maps without even bothering with the Apple maps anymore.
Was curious if things had improved with iOS7, but the incredibly horrible experience of using Apple maps while traveling has me gun-shy to even bother with it at all.