what is better .gaf or .mov for ui animations? or there are other way to give awesome animations with lesser memory.

Hi, I want to use 2d animations in my game. but using sprites make it heavy to load and load. I am starting to use .gaf converter but it uses .swf which is being unsupported by browsers. I am thinking to use .mov or video file for animations but I have limited experience on them. Please Share any other method to implement animation in unity.

Thanks