The identification of the underlying new physics model is one of the main issues of present and future colliders. We are interested in the distinction between different supersymmetric models, the MSSM and the NMSSM. We study tricky cases where the Higgs sector alone is not sufficient to distinguish the models. Exploring the chargino/neutralino sector can be a useful alternative to the Higgs sector. Under the assumption that only the light chargino and neutralino masses and the polarized cross sections $e^+e^-\rightarrow\tilde{chi}^0_i\tilde{chi}^0_j,\tilde{chi}^+_i\tilde{chi}^-_j$ have been measured at a linear collider, we reconstruct through a fit the fundamental MSSM parameters $M_1$ , $M_2$ , $\mu$ and $\tan \beta$. We study whether a model distinction is possible and how additional information can be exploited. We concentrate in more challenging cases in which NMSSM scenarios have a relatively heavy singlino, while we address two classes of neutralino mixing, where neutralino-LSP is either higgsino- or gaugino-like.