Assuming the dual audio 720p version you're referring to is a legitimate release, here's what you can expect:
Dual audio files allow viewers to toggle between languages based on their preference or to help understand specific plot points. Technical Specifications to Look For irreversible2002 dual audio 720p
Allows English speakers to focus on the dizzying visuals without constantly reading subtitles. Perspective: Assuming the dual audio 720p version you're referring