Both TVs come with smart platforms that support popular streaming apps and voice control features. Both TVs provide standard built-in audio performance suitable for regular usage, though external speakers can enhance the experience. Both TVs offer adequate brightness levels suitable for most indoor lighting conditions. Both TVs provide decent motion handling, making them suitable for everyday viewing including sports and action content. TCL 55S451-CA and Haier H55P751UX differ in resolution (UHD vs 4K 3840 x 2160), which can affect overall clarity and sharpness of the display. In general, both TVs cater to modern entertainment needs, including streaming, gaming, and everyday viewing. Both TVs come in similar screen sizes, making them suitable for comparable viewing setups and room environments. If you're comparing TCL 55S451-CA and Haier H55P751UX, both models come with modern features and are designed to deliver a solid viewing experience across different use cases.

Verdict: Both TVs are strong contenders, and your final choice should depend on your preference for screen size, motion performance, and smart features.