We compare in this contribution the analytical approach together with the so-called "end-to-end" approach in the framework of astronomical adaptive optics (AO) modeling. The two tools used for this purpose are well-known and already widely used within the astronomical AO community: PAOLA (Jolissaint et al. 2006, Jolissaint 2010) on the one hand, and the Software Package CAOS (Carbillet et al. 2005) on the other hand. In addition to inter-validate the two codes, trade-offs are clearly searched in order to find optimal compromises permitting to face both exploratory simulations and large instrumental projects while combining effectiveness and certainty.