Dont mean to be rude, but comparison of file sizes of different video containers is pointless. You need to see what audio or video format each of the container files store. Then there could be changes in framerate (fps), frame size (like 640x480), compression quality (or inversely video bit rate), audio bit rate, image encoding (rgb for gif vs yuv420 ). Just changing the audio bit rate from 128kbps to 32kbps for a voice only video (i mean no music, like they have for tutorials) can reduce file size by 50%!