We decided to go for Sebastian's place because of the price and the space of the room. The room proved to be even bigger than it looked and the beds and duvets were nice!
He is easy to get in contact with on phone etc. and very helpful with tips for what to do in Berlin. Sebastian is a chill and service minded person and it felt safe that there were someone living in the apartment as we stayed there. There is no lock on the door for the room, but that never felt like a problem to us at all, because of the calm and safe atmosphere (This room is the only AirBnB-room in the apartment as well).
Would definitely recommend if you are going to Berlin! there is both U-bahn and tram station close to the apartment and quite easy to get around.