Walking tour of Berlin - which company to chose ?

[Frugalit]

Is there a company in particular you can recommend or are they all much of a muchness. Are they actually worth it ?
Fancy world war/ third reich and Cold War ones. Also going to book the Berlin Unterwelt one, heard good reviews about that but not sure which one to go for. Decisions, decisions !

I've done the Third Reich and Cold War tour twice. I booked via Booking.com, but I think the company is called Insider Tour Brtlin. The guides have a pink umbrella and you start at Brandenburg Gate. Both guides were excellent, it's a fascinating tour and really thought-provoking

No idea on walking tour but I did the underworld one at Humboldtthain flak tower, it was really interesting.

Thanks !