The radio model usually used in most of studies on wireless sensor networks is spherical. This means that the received power at a certain distance is the same in all directions. Every radio engineer knows that this is not the case encountered in real hardware. Here, we show that the analysis of such a network by simulation is not trivial when one uses more realistic radio models. We emphasise this problem by comparing the impact of realistic simulations on the study of the infrastructure trade-offs of sensors networks. As expected, simulations confirm that more advanced simulation techniques are required in order to take into account wireless channel models and to bound the simulation time as well.