We present a comparison of observed and calculated Stokes IQUV spectra of two well known magnetic chemically peculiar stars, beta CrB and 53 Cam. The observed Stokes spectra were recently described by Wade et al. (2000a) and have been complemented with additional circularly polarised spectra obtained at the Special Astrophysical Observatory. The calculated spectra represent the predictions of new and previously published magnetic field models derived from the analysis of some surface averaged field estimates (e.g. longitudinal field, magnetic field modulus, etc...). We find that these magnetuc models are not sufficient to account fully for the observed Stokes profiles - particularly remarkable is the disagreement between the predicted and observed Stokes Q and U profiles of 53 Cam. We suggest that this should be interpreted in terms of magnetic morphologies which are significantly more complex that the second-order multipolar expansions assumed in the models. However, it is clear that some of our unability to reproduce the detailed shapes of the Stokes IQUV profiles is unrelated to the magnetic models. For many metallic ions, for both stars, we found it impossible to account for the strengths and shapes of the observed spectral line profiles when we adopted a unique value for the individual ion abundance. We suggest that this results from strongly non-uniform distributions of these ions as a function of optical depth (i.e. chemical stratification), a hypothesis that is supported by comparison with simple chemically stratified models.