From what I've read it doesn't matter too much, it seems like:
1) they'll read through applications 2) if the application looks promising look at the video 3) if the video isn't bad look at the demo
I'm guessing that most of the time they look at the demo they've already mostly decided whether to interview you or not.
(If you don't have any past proof of being able to build things, etc. it might be more important though)
I've seen several people say that when they were at the interview stage the YC partners mostly ignored the demo and focused on questioning.
From what I've read it doesn't matter too much, it seems like:
1) they'll read through applications 2) if the application looks promising look at the video 3) if the video isn't bad look at the demo
I'm guessing that most of the time they look at the demo they've already mostly decided whether to interview you or not.
(If you don't have any past proof of being able to build things, etc. it might be more important though)
I've seen several people say that when they were at the interview stage the YC partners mostly ignored the demo and focused on questioning.