Open method of transportation is subjectable to some environmental risks and hazards. As your car is transported along with other cars, there is a chance of getting scratches and damages. If the concern you choose do not have a well experienced driver, you car is in risk. And if the companies do not have proper gps facility, you may not be able to watch the movement of your car.
As said above, selecting the wrong vehicle transport company may lead you in trouble and if you selected the appropriate one with good reputation and experienced drivers, you are sure that the car reaches to your destination safely.