Whether to choose Radiesse or Sculptra will depend a great deal on how your face is proportioned and what else may be happening with volume loss or genetic volume deficiency.
The face goes through many changes as we age, and this can start very early. Some people are genetically volume deficient in some facial areas. To correct a single compartment on the face, when it may need several to keep the visual "flow", could create more imbalance than correct it.
The temple area is one that can play a huge part in facial balance. A hollowed temple area above newly augmented cheeks could make your face look quite odd. One way to get a better feel for your own facial balance is to trace the outline of a photograph of your face from frontal and profile views. Is your face an inverted triangle? Does one side look higher, wider, than the other?
If your temple area is thinner than the cheek area, you may discover that a rebalance in that area first will provide the right framework for further augmentation in the lower parts of the face. Ideally, a face is five eyes across from the outside of one temple to the other.
If you are sure that the cheek augmentation is all you might need, then Radiesse is certainly an immediate and fairly long term way to address that issue.
Sculptra has the capacity to change the facial balance in a way Radiesse cannot; and instead of relying on implanted material, stimulates your own collagen to produce the "augmentation" effect.