Obviously in pakistan, AFF has a very good reputation and most of the people in ICAP are ex-AFF trainees and plus alot of people in industry holding top positions are also from AFF. So if you plan to stay in Pakistan, AFF is number 1 without a doubt.
2nd is KPMG.. , 3rd EY and 4th Deloitte as per my understanding. KPMG is also a very good firm.. EY gives preference to ACCA's mostly and EY sends its trainees to secondments alot (Dubai, Saudia etc) so if you want to go abroad within your articleship then try to get in EY.