The Yotel rooms on both sides are very basic and very small, but they are perfectly nice and clean. As the others mentioned, airside is priced very high, so since you have a full day/night to relax, I would recommend landside too. I preferred my stay in Arnavutköy just because we wanted to enjoy a few meals in real restaurants and walk around a bit. You can't do this at the Yotel's but they will put you as close as possible to your flight. You can't really go wrong here.