The present work is proposing a comparative analysis of the graphitization, achieved by argon-propane assisted chemical vapor deposition, of 6H-SiC(0001) bulk substrates and 3C-SiC heteroepilayers deposited on (111) and (100) silicon. We have investigated the influence of the experimental parameters of the graphitization (pressure, propane flow rate and duration) both on the structural and the electrical properties of the graphitic/graphene phases developed at the samples surface. In particular, the growth mode has been highlighted. It has been shown that, in our experimental conditions, the formation of graphene is only a transitory step followed by a stage of rapid over-deposition of the surface by a highly disordered graphitic phase. This can be understood by a surface chemical potential variation accompanied by a balance between some mass transport at the surface (which could include sublimation) and a deposition regime. It shows that the process time must be properly adjusted to conserve the graphene at the surface. Furthermore, it is shown that the graphene sheet resistance is significantly dependent on the surface uniformity and can be tuned by varying the process pressure.