In this paper, the impact of array geometry on the direction of arrival (DOA) estimation of spatially distributed sources impinging on a sensor array is considered. Taking into account the coherently distributed source model proposed in [1], we establish closed-form expressions of the MUSIC-based DOA estimation error as functions of the positions of the array sensors in the presence of model errors due to the angular dispersion of the signal sources. The impact of the array geometry is studied and particular array designs are proposed to make DOA estimation more robust to source dispersion. The analytical results are validated by numerical simulations.