Paris everytime for me, here's why:
The Parisians a worse at their jobs so you will do better
The Swiss are better at their jobs and have glass ceilings to keep you in your place.
Geneva is the most boring city in the world, not just bad, I mean god-awful, it makes Lausanne seem interesting and chic.
Paris is 11 times larger than Geneva (2.2m vs 200k) - you will have more top end bars and restaurants down to more macdonalds per sq m to entertain you.
Chances of getting laid in Geneva 1/100
Chances of getting laid in Paris - required by French law. Colleague sex, tourist sex, just-friends sex, politician sex, stranger sex, tramp sex, its all going on!
Chances of having a decent apt in Paris - slim
Chances of having a decent apt in Geneva - slim
Outward bounds opportunities, Geneva wins hands down, the Swiss are made to go to the country for the weekend and ski, cycle, climb or walk it. Paris cannot compete BUT for a restaurant, cafe, bar lifestyle, (see sex above), Paris outdoes GE everytime..
Ease of getting to the airport - Geneva, it can be done
Ease of getting to the airport - Paris, just don't try it, first flight you have to do? Emigrate.
Cost of living differences, France is cheaper and the quality is higher, the average supermarket bill can make you cry in Switzerland. Does Geneva have a Swiss Aldi yet?
French colleagues though are disappointing, I'd choose a Swissie everytime, and they don't let their dogs shit in the street, which is an important point if you don't like to smell of dog-shit all day. I lived in Abbesses in the 18th and walked into the 8th every day and it was a constant dodge.
It does depend on your situation as they are two very different opportunities. Lastly, I would suggest that your two identical work-opportunities are not equal, for example, GE serves a quarter of switzerland, PA serves France, so the career opportunity are surely different.