Dual-polarized (DP) multiple-input multiple-output (MIMO) systems are known to be beneficial in terms of the spectral efficiency under certain conditions on the channel and the signal-to-noise ratio (SNR). In order to assess under which conditions DP antenna setups are advantageous over single-polarized (SP) antenna setups, an accurate yet analytically tractable modeling of such channels is a necessary but challenging task. We propose a novel channel model for DP mobile Ricean MIMO channels for which the statistical channel parameters are readily obtained from a moment-based channel decomposition. An approximate evaluation of the mutual information (MI), expressed as a function of the statistical channel parameters of the proposed channel model, is derived. This approximation allows to assess when it is beneficial in terms of the MI to switch from an SP to a DP setup. Finally, we evaluate the MI for selected SP and DP setups based on channel measurements at 2.53 GHz. We find that the DP setup only provides an improvement in terms of the MI in medium- to high-K-factor scenarios above a certain SNR. The approximate evaluation of the MI is able to accurately reproduce the SNR at which one should switch from an SP to the DP setup.