WordPress MU

Hey All,
I am starting new big site,
I was wondering what was better,
Wordpress MU or Subdomain,
because I want that every new users has there own blog site within my site.
So whats the PRO and CONS,
exemple if I got 10 new users with one is faster to create.

Thanks all
Cyder

"better" in what way?

Either one takes the same amount of time to create a new blog, it's instant.