Aspect Ratio’s 4:3 vs 16:9
Aspect ratio is the relationship of the width of a video image compared to its height. For example 4:3 (traditional TV) or 16:9 (widescreen LCD/Plasma)
Advantages of using 16:9 aspect ratio widescreen format include allowing you to show more content on screen, especially in the horizontal orientation. Also 16:9 format enables you to take full advantage of latest technology used in most hardware today as well as being able to present graphics, video, animation, movies in full widescreen without losing graphical real estate.
Using 16:9 format for your videos and presenations, you are able to show full 16:9 screen content without resizing, stretching or reformatting to fit modern screens and projectors. Almost all video content is now created in 16:9 widescreen aspect ratio, using 16:9 to set-up your powerpoint presentations is suggested to avoid forcing inserted content into a 4:3 aspect ratio workspace where the content will be distorted or trimmed.
If you use 16:9 Content on a 4:3 Screen the screen will show black bars on each side. This is called pillar box effect.
If you use 4:3 Content on 16:9 Screen the Screen will show black bars on top & bottom. This is called letter box effect.