I agree with tepetapan there are many interesting locations along the free roads but when you don't have unlimited time the speed is too slow. So we use the toll roads to get to or near our destinations and use the free roads from then on. Also when you get off the beaten path as we do you only have one choice most of the time, FREE. A downside of the free roads is the increase chance of getting to spend some time visiting with the local police. The only time we have been pulled over was on a free road. Also even if the free road is in great shape there is going to be that hidden Tope out there waiting for you. JMHO!
rocmoc n AZ/Mexico