We have investigated the optical properties of InxGa1xAs/GaAs V-shaped quantum wires (0.1<x< 0.2) by time integrated and magneto-photoluminescence experiments as a function of excitation power density and applied magnetic field at different temperatures. The experimental results indicate the different nature of the radiative recombination processes depending on the In concentration: in the deep quantum wires (x ≥ 0.15) the recombination is excitonic, whereas free carriers seem to dominate in the shallow wires (x = 0.10). We demonstrate that the actual recombination mechanism is primarily effected by the competition between confinement and built-in piezoelectric field which governs the exciton binding energy. Specific theoretical models have been developed to interpret the experimental data.