Side note: on my last day in Berlin I had the choice to wait in line for several hours to visit the top of the Fernsehturm or the Pergamon Museum. I chose the Fernsehturm and regret it to this day.
May I humbly suggest that, if you have to choose, you enjoy the Fernsehturm from the ground (or the sky) and spend your time among the ancient Middle Eastern relics and gates at the Perg. I heard it was amazing.
Check out Uncornered Market’s guide to Berlin for more tips.