This work presents a comparative study of the best models available to describe granular fluids in order to investigate the extent to which it makes sense to speak about a liquid-gas transition in a system of particles that present no attractive interactions. It is shown that the gas and the liquid correspond to regimes with clearly distinct rheological responses. A microscopic interpretation of what happens at the transition in terms of the time scales relevant to the various physical processes is also presented and put the test against numerical data. Our work calls for more experiments to test our predictions on real systems.