Where works best for a nightlife stay?
Hongdae is the easiest place to start when nightlife is part of most evenings and you want bars, music, cafés and late food close to the hotel. Itaewon is a better fit for international pubs and social nights, while Gangnam suits a more polished, higher-budget evening south of the river.
Myeongdong, Mapo / Gongdeok and Seoul Station make more sense when nightlife is only one part of the trip. They trade doorstep bars for easier sightseeing, quieter sleep, airport movement or luggage convenience.