The best resolution for a 40-inch TV largely depends on the viewing distance and personal preferences.
For a typical viewing distance of around 6-9 feet, a resolution of 1080p (1920 x 1080 pixels) should be sufficient to provide clear and crisp images.
However, if you plan on using your 40-inch TV for gaming, streaming high-quality content, or sitting closer than usual to the screen, you may want to consider a higher resolution like 4K (3840 x 2160 pixels) or even 8K (7680 x 4320 pixels) for a more immersive experience.
Ultimately, the best resolution for a 40-inch TV will depend on your specific needs, budget, and personal preferences.