Even Parisians often flee Paris because of red tape and taxes, so if you add a foreign accent, or poor to no French, into the mix you are likely going to be going at a snail's pace. Berlin is cheaper, friendlier to business, friendlier to English and just friendlier in general on the street. The cheapness translates as a factor for employees (their home), and the international orientation of the city allows you to draw on a much broader potential labour force as tons more people from around Europe would consider a move to Berlin than to Paris.

I'd be fairly surprised if there was even a single metric on which Paris beats Berlin for anything business related, so unless you have a product specific to the French market or have a significant other in Paris who can't move it's Berlin every time. Even if you have a product specific to the French market it's probably be best to be outside France unless you need to be there in person to stroke the egos of bureaucrats who might regulate you out of existence.