1600 × 900 vs 1920 × 1080
HD+ against Full HD 1080p, side by side.
1920×1080 renders 633,600 more pixels than 1600×900 — 44% more. Both are 16:9 displays, so content fits identically — the difference is pure pixel density.
A near-forgotten middle step. 1600×900 shipped in budget 17-inch laptops and compact monitors when Full HD carried a premium; that premium is gone, and with it any reason to pick the smaller panel. On used hardware, though, at 17 inches it's tolerable — sharper than 1366×768 ever was.