PhD candidates in France are eligible for 2 types of VISA - Scientific as well as Student. They both have their advantages:
Scientific Visa
- Requires Convention d'Accueil from the host organization
- Spouse of the candidate will be given a scientific dependent visa entitling him/her to work in France till the end of the PhD contract
- Visa is free if the contract is from some National Research Organizations
- Tax Benefits for 2 years. Please see Taxes in France
Student Visa
- Allowed to stay back in France for 6 months after the end of study
- Can drive in France for the entire duration of study with native driving licence (for all other type of visas, the period of driving is only 1 year)
- In many countries to get student visa, application should be through campus france
In short if driving is not your objective, scientific visa is better. Because you'll anyway be getting a student card and with that you will get benefits of students like student residence and all.
GATECSE