This paper compares the interferometric integrated optic gyro (IIOG) and the resonant integrated optic gyro (RIOG). In order to make them comparable, the two kinds of gyros use devices with the same parameters, similar bias modulation methods and planar waveguides with the same footprint and the same propagation loss for Sagnac effect sensing. Firstly, the exact expressions of the shot-noise-limited sensitivities of the IIOG using the square wave modulation and the RIOG using the triangular wave modulation are derived. Then the optimized shot-noise-limited sensitivities of the two kinds of gyros are calculated by optimizing the waveguides parameters. Results show that as the propagation loss of the planar waveguide decreases, the IIOG has better shot-noise-limited sensitivity than the RIOG. As the manufacturing technology of the ultra-low loss planar waveguide develops, the IIOG has much potential in sensitivity improving.