1) Space use: tilt-and-turn windows ventilate without occupying indoor space; at 90° inward they take almost no room, ideal for small flats; the tilt mode opens a small downward angle for ventilation without direct drafts, suited to homes with elderly or children. Outward casements occupy exterior wall space — fine indoors but awkward where balconies or obstacles are outside, especially in high-rise. 2) Ventilation: tilt-and-turn is flexible — fully open for max airflow or tilted to avoid drafts while keeping air moving; outward casements give large ventilation area when fully open but may not fully open in extreme weather or high-rise for safety. 3) Safety: tilt-and-turn operates indoors, avoiding fall risk, with high anti-theft as the sash is fixed on all sides when closed; outward casements risk falling in high wind and often need anti-fall ropes. 4) Sealing and insulation: tilt-and-turn's multi-point locking gives excellent sealing/insulation, blocking noise and dust and holding temperature in winter; outward casements, with good gaskets, multi-layer insulating glass and skilled installation, also form an efficient thermal system. In summary, each has its scene — choose per real need and environment.