Spritesheet vs Video

Is it better to display a low res short clip through a piece of spritesheet or a video player? The resolution is 500×298 and is only about 5 seconds. After slicing the spritesheet in sprite editor, the total file size of the spritesheet is about 6 MB (according to the file size that is shown in the inspector), while the mp4 video clip is only about 558 KB, which is a tremendous difference. But in the game, could the video actually eat more memory or influence the performance even more? I am using Render Texture to play the video by the way. Since we make VFX using spritesheets mostly, I am definitely missing something, somebody explain to me, please.