Advantages of I2C
i. Multiple slave devices can be accessed with only three wires.
ii. Implementation cost is low.
iii. Can be implemented in hardware or software.
iv. Supports multi master configuration.
v. Easy to implement

Advantages of USB
i. True plug and play nature.
ii. Acceptable data rates for many applications.
iii. Low cost
iv. Robust connector system.
v. Variety of types/sizes available