Zafarullah sab,
I think one forum member Muhammad Imran gave very good option of I-8,
You should live in I-8 for 6 months by renting a house then you can easily find out which place is best to live in Islamabad.
Why i am in vafour of I-8, because of some reasons?
(1) I-8 is centre of Real Rawalpindi Islamabad.
(2) There are many good schools in H-8 education sector which is nabour of I-8.
(3) Shifa international Hospital located on doorstep of I-8.
(4) There are too big parks located in I-8.
(5) Pindi/Islamabad 2nd biggest inter city bus station Faizabad bus station located on door step of I-8.
(6) The ongoing Metrobus project is passing close to same sector.
(7) The most important thing the worth of your property will never drop it will constant increase because of its location.
(8) From I-8 you can opproach to any place of Pindi/islamabad with 360 degree in minutes.
Remember three golden words to buy a property, location,location and location.
There is no competition of location in property buisness.
ZONE-1 is the heart of Islamabad no other Zone can replace this zone in present and in future.
You will find best devolpement standard in Bahria,DHA or B-17 but Still CDA is dominating on Bahria,DHA,B-17 and others housings because of location.