On behalf of Ryan Curran. This is a bit of a tough question to answer because it depends upon design decisions. Typically, the SDA line (data line) requires a pull up resistor for when the SDA line is released from the bus and in high impedance mode. The sizing of this resistor will determine the power consumption of the I2C interface. As a rule of thumb, SPI is better for high speed and low power applications while I2C is better for suited for communication with a large number of peripherals and dynamic changing of the master device role among the peripherals on the I2C bus.
