We make a comparative analysis of rhombohedral perovskites (ABO3) with/without oxygen rotations and ionic shifts, within the framework of a generalised effective field approach. We analyse available data on LaAlO3 and LiTaO3 and new data on Zr-rich PZT, examples of three different ways of structural evolution with temperature of the rhombohedral perovskites. The coupling between polarization and tilt is studied in detail in PZT and a possible coupling between tilt and polarization in LiTaO3 is discussed.