What’s the different between branded power bank and generic power bank?

Branded power bank mostly sell in REAL CAPACITY. Generic power bank mostly sell in MARKING CAPACITY. That’s the reason why you will never see any branded power bank (standard size) have anything as high as 30000mAh – 50000mAh. That’s also the reason why a good 12000-13000mAh power bank are able to charge more or about the same like the market 30000-50000mAh power bank.