Choose SAW when it fits the actual flight, accommodation and onward direction. A flight arriving at SAW cannot be paired casually with an IST collection: crossing the metropolis needs a separate transfer and booking plan.
The airport places rental offices on the arrivals level of the terminal. Use the booked company’s voucher to locate its desk and vehicle, and confirm late-arrival and return conditions rather than assuming published terminal opening information covers your reservation.
A rental car is useful for regional journeys along the Aegean and Mediterranean coasts or for a separately planned Cappadocia stay. For central Istanbul, compare public transport and collect the car after your city days instead of paying to park it throughout the visit.
Compare airport collection with a later collection if you start with a city stay. Include the transport to a different rental branch and any extra parking nights when comparing the total cost.