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 (39 Inch (99 cm) vs 40 Inch (102 cm)), and a larger screen generally provides a more immersive viewing experience. Both TVs come with smart platforms that support popular streaming apps and voice control features. 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. Intex LED-3900 and Sansui SJX40HB21CAF differ in resolution (1920 x 1080 vs 1366 x 768), 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. Intex LED-3900 and Sansui SJX40HB21CAF are well-equipped smart TVs that aim to provide a balance of picture quality, performance, and smart capabilities.

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