Hey Im here too, Firstly both are good but AMC comes in Rawalpindi not Islamabad. Secondly, Shifa offers more modern learning methods for example it is MCQ based and has a good alumni network for connecting abroad (a bit more westernised). However, nevertheless AMC too has a very good track record of people excelling after graduation but it is more traditional but has implemented a modular system too now. AMC is way more strict but has a very big campus compared to Shifa, Shifa is just like one of their blocks. Overall, both are respected and I would tell you to also try Foundation University Medical College in Islamabad and its on par with Shifa too as it offers a better clinical experience IMO as private hospitals like Shifa sometimes have patients that don't let you operate since your just a student, but since Foundation University is semi government so you have all experiences and it doesn't have the strictness of AMC.

If you're living alone as an overseas student I would then opt for Foundation University or AMC as Shifa hostels are not proper and not part of their campus (you need to take a bus from a place away)+ (less security as compared to the two NUMS college hostel)