Definitely in former East Berlin if you wanna be where the action is
The first time I visited I stayed at the Circus Hostel near Rosenthaler Platz. Most recently with the Mrs. we stayed at the Arcotel John F near Museum Island. Would recommend both for entirely different reasons
Both are in the Mitte area. Other "hipster" areas would be Kreuzberg or Prenzlauer Berg
It's been ages since I stayed in Amsterdam but it was a hostel. Kind of a dump from what I remember though so can't recommend it.