With SPI, the MOSI line always transmits data from the master to the slave, and the MISO line always transmits data from the slave to the master.
With I²C, there is only a single data line for both direction. The R/W bit controls which device transmits data bytes and with device transmits the ACK bits, but the R/W bit itself is always controlled by the master. (The R/W bit can be changed with a repeated start condition, but only by the master.)
And the clock is always controlled by the master. (An I²C slave can delay clock cycles with clock stretching, but it cannot generate new clock cycles.)