They must explain or account for similarities and differences in the characteristics of the planets. The sun's equator lies roughly in the ecliptic Planetary orbits are nearly coplanar. All planetary orbits are prograde. Planetary orbits are nearly circular. Many Satellite orbits are prograde.
Most planets rotate prograde.
Overall abundance ratios of chemical elements in the Jovian planets are like those in stars. Jovian planets are further from the sun than terrestrial planets. Oldest planetary surfaces are heavily cratered. Some planets rotate much more slowly than others. Planetary rotation axes seem to have no preferred orientation to the ecliptic.