Ok and Turtle. This discussion isn't even a fair one. You work for a reputable company. Of course your miles are correct.
Yeah, but don't forget I used to be leased to Panther, where the road miles rarely matched the billed.
OK, so by "accurate," you mean that it more closely matches the actual driven miles. Sometimes you have to be specific, because there are some routing options where 5 miles on their map is actually 4 or 6 when you drive it. Tom Tom, Lowrance and Magellan all have "measurement" issues with regard to accuracy.
Like Moot said, PC Miler Practical is very accurate compared to the actual driven miles. It must accurately routes trucks on the truck preferred roads, and avoids roads that tricks should probably steer clear of. Google Maps assumes you're in a car, not a truck.
PC Miler Shortest uses the shortest truck route. The Household Goods Miles version of PC Miler uses the shortest route on which trucks are not explicitly forbidden. This can include unpaved roads, particularly out west.
Google Maps is pretty good for routing vans, but not to much for trucks. But even in a van, Google Maps will flat route you on a Parkway in New York and New Jersey, so ya gotta watch that, especially if you use Google Maps for mileage billing.