i stayed nearly 20 days at that house. firstly i should say that kristina is very kind owner. about house; location is perfect, you can go centre of kadıköy by walk in 8-10 minutes (there is a lot of bars, coffees and restaurants). there is a big park in front of the house an you can feel peace when you stay near the window. if you have a car, it is not so hard to find a parking area for your car (normaly finding a place for your car is very difficult in istanbul).
I can advise you to add this house between your choices.