According to the Law of People's Republic of China (PRC) on Mediation and Arbitration of Labor Disputes
Twenty-first labor dispute arbitration committee is responsible for the jurisdiction of labor disputes.
Labor disputes shall be under the jurisdiction of the labor dispute arbitration commission at the place where the labor contract is performed or where the employer is located. Where both parties apply for arbitration to the labor dispute arbitration committee in the place where the labor contract is performed and the place where the employer is located, it shall be under the jurisdiction of the labor dispute arbitration committee in the place where the labor contract is performed.
It is clearly stipulated in the clause that the arbitration shall be conducted at the place where the contract is performed/the place where the unit is located. That's where your company is located, not where it is registered. So you should go to Fengtai.