The LG 77B4 OLED outperforms the LG 75NANO75 with perfect blacks and 120Hz refresh (per RTINGS contrast and motion scores) while the Nano75 reaches only 1200:1 contrast and 60Hz. The B4 also supports four HDMI 2.1 ports versus two on the Nano75. Choose the B4 for dark-room viewing or gaming; the Nano75 suits bright rooms needing larger size at lower cost.