If I would visit Sofia for a few days - this will be may stay of choice because:
1. The apartment has everything I need - brand new furniture, wi-fi, parking place, fully equipped kitchen.
2. Main sights in proximity - the ancient ruins of Serdika, the Parliament and the the old public baths - 5-7 min walk. The pedestrian area of Vitoshka - 10-12 min walk.
3. A traveller host - Ned has travelled extensively and Airbnbs have been his second home. So he tailors his apartment accordingly.