Estimating pore pressure development in liquefiable deposits is very important to predict liquefaction consequences at the surface namely in terms of damages to structures. Several simplified methods have been proposed from which the stress-based method from Seed et al. (1975) is the most widely used, due to its simplicity. Various attempts have been made however to develop an energy based method that could avoid the conversion to an equivalent loading, trying to quantify the liquefaction resistance in terms of a measure that reflects the true nature of seismic shear wave loading. This paper investigates the advantages and limitations of stress-based and energy based methods. For that purpose, effective and non linear dynamic numerical analysis were performed and compared with the simplified methods showing the parameters needed in each method, its assumptions and simplifications and its consequences in terms of the pore pressure prediction.