visited these places last year. it is best to travel on a hired Prado or 4x4. It comes handy when maintaining the average speed. On a patchy road, you cannot go more than 30-40 on a car but prado can actually maintain up to 60 without much problem. Also, car will take a lot of wear and tear and in case of any engine problem, you wont be able to find workshop who has good knowledge of efi engines. Further, petrol is not easy to get. even if it's available, remember there are chances that it's not very clear and EFI cars are sensitive. Diesel is available easily.
it's better to take a hired car to have a tension free trip.