Capsules win when the dose is small, the ingredient blend is bitter or unpleasant, or the brand wants a clean-label positioning without excipients. Two-piece capsules also allow bead-in-capsule and multi-ingredient layering that tablets cannot easily replicate.
Tablets win on unit cost at scale, on high-dose actives (above roughly 800 mg per serving), and on release-profile control — enteric and time-release coatings are far more mature in tablet form than in capsule form.
Where brands most often get this wrong: high-dose greens or protein blends in capsules. A 6-gram daily dose in a size 00 capsule requires 12+ capsules per day, which nobody actually takes. That is a powder or a tablet, not a capsule.
For borderline cases, ask us to quote both. The unit-cost delta at your target volume is usually the deciding factor.