salam to all. in my opinion there is a trade off regarding residence either you go for the short distance or for better facilities. I lived in Islamabad for 6 years 2006-2012 that's why have some knowledge. near university there are so many hostels but they have such facilities in which only a student can adjust hahahaha means tough conditions. distance wise areas which are a bit better:
1- shahzad town
2-abpara
3-g6
4-18
5-g8
6-i9
7-i10
the place where comsats is located is like village or suburbs of isb.
so boys trade off as per your choice.
and girls if you are looking for security then my opinion is near to comsats area is not suitable for you because of the student hostels all around. for girls I would suggest you to opt the girls hostels located in above mentioned areas which do have security guards and female staff.

note: f-6 and f-7 can also be an option but if someone wants a luxury type accommodation. secure and clean but will be like you are doing job and pay is going to someone else hahahahahah much expensive.