1280 × 720 vs 1920 × 1080
HD 720p against Full HD 1080p, side by side.
1920×1080 renders 1,152,000 more pixels than 1280×720 — 125% more. Both are 16:9 displays, so content fits identically — the difference is pure pixel density.
720p still makes sense in three places: small TVs viewed from across the room, budget projectors, and streaming over slow connections where the lower bitrate matters more than pixels. On anything you sit close to — a monitor or a laptop — 1080p is the practical minimum, and the upgrade is immediately visible.