when i download film same 720p film have different sizes on different torrents?

[Nancy]

ok so i type on torrentz.com a film name and list of torrents appear
the same 720p film is 400mb whereas below that on another result(just like google search results) the film can be 1gb or if bluray then it maybe more, but that film is not blu ray INFACT IT CAN HAPPEN FOR ANY FILM THAT THE SAME PRINT THE SAME EVERYTHING ONE IS 4GB TE OTHER 400MB

THEN WHY THE HELLLLL SHOULD I DOWNLOAD LARGE FILM WHEN RESOLUTION IS SAME??????
DOES IT HAVE ADDITIONAL SAFETY OR STH LIKE THAT

[K]

You said resolution is same 720p for 400mb and 4gb. They may have ripped choosing different codecs in different formats, multiple languages, 5.1 channel audio
But Clarity will be more (Audio and Video) in 4gb when compared to 400mb. It depends on how talented the ripper is.