Resin (SLA / MSLA) — when detail and surface matter. Collector figurines, casting jewelry, dental models, micro-mechanics. Layer from 25 μm, near-glass smoothness.
Filament (FDM / FFF) — when the part needs to be strong and larger. Electronics housings, machine parts, functional prototypes. Materials: from soft TPU to carbon-fiber nylon.
Don't use resin for: UV-exposed parts (they degrade), very large models (max 300×200×200 mm in one piece), mechanically stressed parts (brittle).
Don't use filament for: figurines under 30mm with micro-detail (layers visible), jewelry for precision casting, perfectly smooth surfaces without post-processing.
Rule of thumb: 'will I paint and display this' → resin. 'will I use this' → filament.