Zhixing, which is more cost-effective, platinum or black diamond?

It depends. According to official website information of Zhixing train ticket, Platinum members can enjoy privileges such as airport VIP lounge, high-speed rail VIP lounge, free visa agency, car rental discount and hotel discount. Black Diamond Card can enjoy 10% discount on ticket purchase, ticketing service, exclusive customer service, higher discount, more points return and other privileges. Buy a black diamond card for frequent business trips and a platinum member for occasional business trips, so it depends on the frequency of use.