Sufi Bhai is right. I also like 2nd route. Its much more beautiful. Climbing Murree hills from one side (Islamabad) and going down to Abbottabad. From Nathiagali to Abbottabad, its a down hill ride all the way.
Between Ayubia chowk and Nathigali, there is a place called MOORTI. you can read sign board. It's about 3-4 kilometers from Ayubia chowk. Just sit there for few hours and see lush green valley down there. Its like Switzerland.
I took this pic myself at Moorti.
On a side note, I would like to say that your driver should be experienced. Do not use brakes too much when going down hill. use gears. Many people from Lahore and southern punjab (plain lands) do excessive braking which results in brake problems. Natiagali climb is a bit steep.
You will enjoy this route as it is less hectic than going all the way to Naran.