Hi GC - Great question. Processing & Picture: The QN990F features our advanced NQ8 AI Gen3 Processor and Auto HDR Remastering Pro, giving it increased clarity, brightness, and HDR performance. Both models feature our Glare Free tech; both are great options for bright rooms. Motion & Gaming: The QN990F supports up to 240Hz (165Hz on QN900F), plus AI Motion Enhancer Pro for extra smooth action. Audio: QN990F has 90, 6.2.4Ch audio with Object Tracking Sound Pro vs. 70W, 4.2.2Ch & OTS+ on the QN900F. Design & Connectivity: QN990F introduces our new Wireless One Connect for a cleaner setup and an incredibly sleek Infinity Air/Zero Bezel design. The QN990F also features a center stand (2-legged on QN900F) and adds a 5th HDMI port (4x on QN900F).
~ Samsung Specialist