I lived in Stuttgart from ‘94 to 2004, then Munich from 2004 to 2014 and have been in Berlin since 2014. All moves were job related. I actually enjoyed my time in Stuttgart (I lived in Böblingen and worked in the city). However, it took me about two years to make any real friends (they say the Schwaben are slow to warm to someone from the outside), but they are now still some of my best friends today and we had really good times together. I also enjoy hiking, skiing and motorcycle riding, so the surrounding countryside was ideal for my purposes. That said, it is more of a sleepy provincial town, money/materialism seem to be very important to some and much of the city is really quite ugly and staid.
Munich was great and I love the city, probably my favorite city along with Prague.
Berlin is definitely the polar opposite. It is indeed edgy and more international. I have a love/hate relationship with Germany’s capital as I definitely appreciate cleanliness, efficiency and law and order and a lot of this is lacking here. However, it’s a big city and you can pick and choose how and where you live. For instance, in my part of town it’s a lot like Schwabing in Munich, which was what I was looking for when I bought a place four years ago. Public transit is very good here too, albeit very scuzzy compared to Stuttgart and Munich, and there is quite a cultural offering to be had.
A former colleague worked in Berlin for about two and half years before joining the competition in Stuttgart and thereby essentially doubled his salary overnight. However, the novelty of the new city soon wore off for him and he longed to come back. Then in January of this year he got his firm to transfer him to the Berlin branch with his Stuttgart salary. He has no regrets leaving. He also said that downtown Stuttgart has recently been taken over by the “Party- und Eventszene” and become rather seedy.
From what the OP has written, I would advise against him relocating to Stuttgart unless the job opportunity is just too good to turn down.