I know Berlin as well as Köln from several stays at each.
The selection at Berlin is slightly better then Köln, there is always a cheese selection in Berlin, which is not available in Köln. There is always Sushi in Berlin, which is not the case in Köln. There is much more drinks availability in Berlin then in Köln.

I also prefer the seating in Berlin, although the view in Köln is better.

I would say these two lounges are actually both pretty good but I see a clear advantage in Berlin.