What's the difference between Shantou and Shenzhen FOB?

Of course not. The most obvious thing is that the towing fee is different. In the case of fob Chaozhou, your towing fee is from your factory to Chaozhou (Shantou) port, while in the case of fob Shenzhen, your factory is from Shenzhen (Shekou/Yantian) port. The cost of the trailer varies greatly. Moreover, port charges are different, such as port construction fees and customs declaration fees.

Since there is such a price difference, if you apply for FOB Chaozhou, you'd better launch in Shantou, or you'll die.