  We present a comparison of the tunnel magneto-Seebeck effect for laser
induced and intrinsic heating. Therefore,
Co$_{40}$Fe$_{40}$B$_{20}$/MgAl$_2$O$_4$ and Co$_{25}$Fe$_{55}$B$_{20}$/MgO
magnetic tunnel junctions have been prepared. The TMS ratio of 3\,\% in case of
the MAO MTJ agrees well with ratios found for other barrier materials, while
the TMS ratio of 23\,\% of the MgO MTJ emphasizes the influence of the CoFe
composition. We find results using the intrinsic method that differ in sign and
magnitude in comparison to the results of the laser heating. The intrinsic
contributions can alternatively be explained by the Brinkman model and the
given junction properties. Especially, we are able to demonstrate that the
symmetric contribution is solely influenced by the barrier asymmetry. Thus, we
conclude that the symmetry analysis used for the intrinsic method is not
suitable to unambiguously identify an intrinsic tunnel magneto-Seebeck effect.
