Apartments offer a much more genuine experience of Istanbul, much more space, your own cooking area but on the other hand hotels offer you a daily house keeping service, breakfast, on-site staff but nothing comes free in the life! The other side of the coin, you pay for these hotel services although you might not need them! Do you really need your room to be tidied up everyday? Isn’t it a bit boring to eat hotel breakfast at the same restaurant every single morning? Your accommodation need depends on your personality of course. Also you might say that hotels don’t charge extra for these services but don’t forget all of the hotel services are reflected in hotels prices. This is why much tiny hotel rooms costs much more than spacious apartments!
Apartment accommodation in Istanbul Turkey is much rare comparing to hotel accommodation but it is worth to try to check.