Hi,
It is also best to have a carte de sejour in France as it covers you in many requirements. When applying for anything, they request it. This system is already so complicated, that if you present them with a non-French document, it will make your life a whole lot more difficult.
I think you also need it to work in France, even if you are an EU Citizen.
When you apply for the Carte de Sejour, you will be given a récepissé, which will act as a Carte de Sejour, until one is issued to you. Also, you will have to renew this every year for 5 years, after which you can request one for 10 years and perhaps even the nationality.

Best of luck.