The Samsung QN55QN90B is the clear winner in this head-to-head battle. With superior HDR peak brightness, more refined local dimming, and premium processing that delivers jaw-dropping contrast and color accuracy, Samsung's Neo QLED simply outperforms the TCL QM851G in almost every picture-quality metric that matters to serious home theater enthusiasts.

Quick Specs Comparison

Brightness and HDR Performance: Samsung Dominates

In benchmark HDR peak-brightness tests, the Samsung QN55QN90B pulls ahead decisively with sustained highlights reaching nearly 2000 nits compared to the TCL QM851G's respectable but lower 1500 nits. This isn't just a number on a spec sheet. That extra 500 nits translates into highlights that pop with more intensity in scenes from movies like Blade Runner 2049 or The Meg. Samsung's Mini-LED backlight combined with its advanced quantum dot layer produces HDR that feels more cinematic and lifelike.

The TCL QM851G is no slouch and can deliver impressive brightness for its price point, especially in larger screen sizes where it scales well. However, Samsung's superior anti-reflective coating and higher peak output make it far more watchable in brighter living rooms. If you're chasing that reference-level HDR punch that makes Dolby Vision and HDR10+ content sing, Samsung is the undisputed champion here.

Contrast, Black Levels, and Local Dimming

This is where the real battle happens. Both TVs use Mini-LED backlighting with thousands of dimming zones, but Samsung's implementation is simply more intelligent. The QN90B exhibits fewer blooming artifacts around bright objects on dark backgrounds. When watching high-contrast content, Samsung maintains deeper, inkier blacks without the haloing that occasionally plagues the TCL QM851G.

TCL has made massive strides in local dimming algorithms with the QM851G, and at its price it's impressive. Yet side-by-side comparisons reveal Samsung's Neural Quantum Processor 4K makes smarter real-time decisions about zone control. The result is contrast performance that feels closer to OLED without the brightness limitations. TCL fights back with larger available screen sizes (up to 98 inches), making it the king of value for those wanting an enormous canvas for movie nights.

Gaming Features and Motion Handling

Both TVs are excellent for gaming, supporting 4K@120Hz, VRR, ALLM, and low input lag. However, Samsung edges out with four full HDMI 2.1 ports versus TCL's two. This matters if you own multiple next-gen consoles and a high-end PC. Samsung's Game Bar is also more polished, giving you quick access to settings without interrupting gameplay.

Motion handling is where opinions might split. The TCL QM851G offers a 144Hz gaming mode that some PC gamers will appreciate, and its motion smoothing is quite good for sports. Yet Samsung's Auto Motion Plus processing delivers more natural-looking motion without the soap-opera effect that cheaper TVs struggle to avoid. For sports fans and gamers alike, Samsung simply feels more premium and responsive.

Smart Features, Sound, and Build Quality

Samsung's Tizen platform remains one of the snappiest and most intuitive smart TV interfaces available, with excellent app support and seamless integration with SmartThings for home automation. Google TV on the TCL is no slouch and actually offers a more open ecosystem with better Chromecast support, but it occasionally feels slightly less polished.

Audio performance is surprisingly strong on both. Samsung includes its Object Tracking Sound technology that follows action across the screen more convincingly. TCL counters with solid built-in speakers and support for Dolby Atmos. Neither will replace a dedicated soundbar for serious cinephiles, but Samsung again feels like the more refined package.

Who Should Buy Which?

Buy the Samsung QN55QN90B if:

• You prioritize absolute picture quality and HDR performance above all else
• You have a brighter room where peak brightness and reflection handling matter
• You own multiple HDMI 2.1 devices and want future-proof connectivity
• You're willing to pay for premium processing and build quality
• You want the best 55-65 inch performance without compromise

Buy the TCL QM851G if:

• You want maximum screen size for the money (85" and 98" models offer incredible value)
• You're shopping on a budget but still want flagship-level Mini-LED performance
• You primarily watch in controlled lighting where 1500 nits is more than enough
• You prefer the Google TV ecosystem and voice assistant
• Price-per-inch is your most important metric

Final Verdict

The Samsung QN55QN90B is the superior television. Here's why:

• Substantially higher peak brightness (2000 nits vs 1500 nits) creates more impactful HDR
• More refined local dimming with fewer blooming artifacts and deeper blacks
• Better overall processing and color accuracy out of the box
• Superior gaming connectivity with four HDMI 2.1 ports
• More polished smart platform and motion handling

That said, the TCL QM851G is the value champion. For buyers seeking massive screens on a budget, especially in larger living spaces, TCL delivers an experience that punches well above its price class. The gap between these two isn't enormous in absolute terms, but when you're spending thousands on a premium TV, those differences become meaningful.

At the end of the day, Samsung earns the crown for picture performance while TCL wins on value and sheer size options. For most discerning buyers who can stretch their budget, the Samsung QN90B is the TV worth owning in 2023 and beyond. Its 8.6/10 score versus TCL's respectable 7.8/10 tells the real story: Samsung delivers the more impressive, future-proof viewing experience.