Audio output differs between the two (10 W + 10 W vs 30 W), which can influence overall sound clarity and loudness. There is a difference in screen size (58 Inch (147 cm) vs 55 Inch (139 cm)), and a larger screen generally provides a more immersive viewing experience. TCL 58S455-CA and Mi TV X55 are well-equipped smart TVs that aim to provide a balance of picture quality, performance, and smart capabilities. Overall, both models are capable choices in their segment, offering a balance between performance, features, and usability. Both TVs offer adequate brightness levels suitable for most indoor lighting conditions. TCL 58S455-CA and Mi TV X55 differ in resolution (UHD vs 4K 3840 x 2160), which can affect overall clarity and sharpness of the display. Both TVs come with smart platforms that support popular streaming apps and voice control features. Both TVs provide decent motion handling, making them suitable for everyday viewing including sports and action content.

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