I don't know how the OneNote app works (I seem to have misplaced my Windows Live ID), but as I recall, it does have one less step. Is it faster, though? I don't know. In Evernote I can see my last note as soon as I open the app, so that is the same. If I want to add something, though, I do have to press the pencil icon at the bottom, unless I left the note open.
Anyhow, assuming there is a one second difference, then you are saving time with OneNote! The cool thing for me is that I can pull out my computer, iPad, iPod, Macbook, or Android phone and view the note 🙂