Both TVs provide decent motion handling, making them suitable for everyday viewing including sports and action content. Both TVs provide standard built-in audio performance suitable for regular usage, though external speakers can enhance the experience. There is a difference in screen size (43 Inch (109.22 cm) vs 40 Inch (102 cm)), and a larger screen generally provides a more immersive viewing experience. Both TVs offer adequate brightness levels suitable for most indoor lighting conditions. Both TVs come with smart platforms that support popular streaming apps and voice control features. TCL 43S451-CA and TCL 40S5400 are two competitive smart TVs offering a mix of display performance, smart features, and overall value for different types of users. TCL 43S451-CA and TCL 40S5400 differ in resolution (UHD vs 1920 x 1080), 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.

Verdict: Both models offer good value, and the better option depends on your specific requirements and viewing preferences.