Not sure if this helps or not but I'll just throw it out.
We just went on vacation and we used MapQuest and Goole Maps to figure out the fastest route at the start of the trip. Distance wise they were both about the same. Time with Map Quest saved us 20-30 minutes which was a good chunk of time.
Not sure how you can figure out which GPS unit can give you the best route. The roads we took are not new. Map Quest for some reason had a better route.
And a GPS does not keep you from getting lost.
We live at the end of a road. We own the last 1000 feet or so and have a gate across the road. This week the gate was open and I could hear some heavy equipment moving our way....
Turned out it was a semi with a load of trusses.

The driver had just drivin to a dead end on a single lane gravel road and realized he was having a Huston we have a problem moment. He turned off the big rigs engine.
The trusses were too big for what I need to build but I could make 'em work. And I told him so. He grinned.

He kinda mentioned his directions but not all of them so it sounded like he just had the wrong directions. The road he was looking for was familiar but I could not figure out where it was. He made some phone calls and got now where.
He wanted to back out a half mile down a windy single lane gravel road.

I finally convinced him that the grass and moss covered open area was really full of gravel and he would not get stuck. He turned around and left.
Got up to the house and talked to the wifey and told her about the road. She looked at me and said it sounds like he was trying to get to the subdivision on our western border.

DUH! I felt like Homer. His instructions told him to make a left turn from town. He turned a half mile too soon. He did not read me all of the directions if he had I would have figured out where he was trying to get. He was only about 2,000 feet from his destination as the crow flys. It was just due west.




To get that truck there he was going to have to drive a couple of miles.


Later,
Dan