SiC-based IMPATTs with its different polytypes (3C, 4H, and 6H) are modeled, designed and a comparative study among three are presented in this paper to operate at D-band frequency at the same operating conditions and frequency of operations under static and dynamic conditions. A noise analysis model was also developed to compare the noise characteristics of 3C, 4H and 6H SiC-based IMPATTs. The results show that 3C-SiC based IMPATTs have better power delivery capability whereas 4H SiC-based IMPATTs are less noisy. Hence a noise-power trade-off method is used to determine the potential of each polytypes of SiC-based IMPATTs.