Material selection depends on the purpose of the impression, required accuracy and dimensional stability, moisture control, undercuts, tray design, working and setting time, disinfection, laboratory transport and patient tolerance. Alginate is economical and useful for many preliminary impressions but should generally be poured promptly. PVS provides high accuracy and stability for many definitive impressions. Polyether is accurate and relatively hydrophilic but can be rigid in undercut areas.
Review the comparative guide: dentalreach.today/types-of-impressions-and-impression-materials-in-dentistry
Which clinical factor most often determines your material choice: moisture, undercuts, accuracy, patient comfort or laboratory workflow?