速度不一样，价格不一样。

USB3.0 is up to 5Gbps enough for fastest Hard Drive, USB2.0 is up to 480Mbps so is slower than many SATA drive and flash drive now.

However, for a flash driver that is small in size, 8G, 16G, USB2.0 is good enough as you won't transfer large files anyway.

USB2.0 has only about 40Mbps or less when continuous transfer due to its bad, poor, silly protocol.USB3.0 might be better but still not as good as SATA3.0 etc.