Silicon carbide (SiC) nanowires (NWs) could combine the properties of one-dimensional (1D) structures with those of a wide band gap semiconductor. For this reason, we solved self-consistently the Poisson equation with both the quantum Non-Equilibrium Green Function Formalism (NEGF) and the classical drift–diffusion model in order to model and compare 3C-SiC and Si NW Field Effect Transistors (FETs) operating in ballistic and diffusive regimes. As a general conclusion from our calculations in the ballistic regime, Si and SiC NW FETs have almost the same electrical behavior. They show the same subthreshold slope and have similar on-current (I_ON/I_OFF (SiC) ~81% I_ON/I_OFF (Si) in the case of a 4 nm NW cross-section side). The drift–diffusion model predicts a better performance for SiC NW FETs. More specifically, SiC devices have a lower subthreshold slope (~85% for a Si device with 200 nm channel length) than Si devices as the FET channel length increases (from 200 to 750 nm), and as in case of ballistic regime SiC devices have a slightly smaller on-current.