Four-mirror telescopes of the same configuration, once employing a spherical and the other time employing a parabolic primary are compared with respect to their performance, and the alignment sensitivities of the three correction mirrors. This is done for three different primary focal ratios, F/1, F/.8 and F/.6. The systems with parabolic primaries provide a far superior wide field performance, and are less sensitive to misalignments of the tertiary and quarternary mirrors. The spherical primary systems are highly corrected over a much narrower, though, for many applications possibly sufficiently extended field of view. The attractiveness of the spherical primary is the simplicity of its fabrication, and if segmented, also the largely simplified alignment procedure of the segments.