But corporate tax alone is not a good way to evaluate the opportunity of creating your company in France.
As a startup you are supposedly doing innovative stuff and R&D so you actually get tax credits[0]. Crédit Impôt Recherche &Crédit Impôt Innovation brings you up to 30% of your R&D investment.
As a startup in France you are eligible to the Jeune Entreprise Innovante status which basically means you pay nearly no social contributions on the salary of your R&D personnel (which is a huuuge amount: as a rule of thumb, total cost of 1 salesperson is roughly twice his/her net salary. Paying half of that for your engineers is...cool).
As a startup in France you also get grants from BPI (Banque Publique d'Investissement) and colateral for your private loans.
As a startup in some regions of France you can get local grants which can be a huge amount as well (and Paris is not one of them).
If you want to try to get into the French Tech Ecosystem, there is a program similar to Startup Chile, French Tech Ticket[1], but the grant is only 25k€
To give an anecdotal example, I raised south of 1M€ of private equity (which is obvious a very small amount by US or european standards), but I got almost as much public grants/tax credits/local help. My colleagues/competitors located in the Paris region got substantially less local help for the same amount of money raised and comparable market/R&D programs.
[0] http://cache.media.enseignementsup-recherche.gouv.fr/file/CI... [1] http://www.frenchtechticket.com/