My Garmin (that I no longer use) tried to get me to take a 4 wheel drive road over a mountain pass into the back entrance to Great Sand Dunes NP. But Streets and Trips took me to a rough rock low water crossing also needing 4x4. And my trucks built in GPS gives crazy directions sometimes. And just took a trip with a friend in his brand new GMC Denali and his built in GPS was also giving directions we knew were far from the best. No matter which you use, always know in advance the approximate route before you get there.
I use mine primarily for ETA, miles to next turn, lane change info, and finding a specific address after I am already near that point.