Both TVs provide decent motion handling, making them suitable for everyday viewing including sports and action content. Both TVs come with smart platforms that support popular streaming apps and voice control features. Insignia NS-39DF310NA21 and Westinghouse WH40FX51 are two competitive smart TVs offering a mix of display performance, smart features, and overall value for different types of users. Overall, both models are capable choices in their segment, offering a balance between performance, features, and usability. Insignia NS-39DF310NA21 features a 39 Inch (99 cm) screen while Westinghouse WH40FX51 comes with 40 Inch (102 cm), which can make a noticeable difference depending on your room size and viewing distance. Insignia NS-39DF310NA21 and Westinghouse WH40FX51 differ in resolution (1280 x 720 vs 1920 x 1080), which can affect overall clarity and sharpness of the display. 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.

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