I can totally understand the people who say that TXL has it advantages in terms of street-to-gate-time. That is something you will experience in a number of small airports.

But this is the only positive thing you can say about TXL.

Everyone who has (or wants) to use public transportation needs as much time to get to TXL as you will probably need to get to BER. The terminal is often totally crowded and blocked by the lines of people at check-in. The building is crap and the number of fingers is very low. The numbers of pax every year is far above the planned capacity and you can feel that.

We don't know what will happen in BER. I am sure, that during the first weeks there will be a lot of problems - of course. But in the long run, BER will be the better choice for the overall passengers.