If you throw both a curveball and slider, they are generally better if they have different movement profiles. This was definitely the case for Kyle Freeland in 2021, where those breaking pitches were separated more than ever:
The above charts represent vertical and horizontal break, and the light blue circles show the curveball Freeland has thrown since 2018 (in succession, right to left). Pay attention to how far those blue and yellow (slider) circles have grown apart.
Freeland throws five pitches (curveball, sinker, slider, fastball and changeup).