Take a look at this thread for hotel stopover questions. The hotels TK used are all back near the city and old airport.

TK in IST: Thread #3 - Transit and Stopover Hotel, Touristanbul, Sleeping Rooms

This will also give you information about the use of the lounge sleeping rooms (based on layover length). nvm, a 19 hour layover is too long to be given a sleeping room.

Sleeping in the lounge is a hot button topic and the lounge is not conducive to sleeping.

The Airside Yotel is very convenient, but very costly. With that said, that's my go-to move. It's Airside, near the lounges and clean and comfortable.