I'm using Evernote 7.14 on a Mac. I agree that the Mac client seems to be missing this configurable option, it would be great to see it added. That said, I think the logic behind whether or not a new window opens when you start a new note is what view you're currently on in the main window. If you're looking at a Notebook, or at All Notes, starting a new note adds it to the currently viewed notebook, and the UX continues in the main window without a popup. However, if you're viewing notes by tag, starting a new note pops up a new window. I guess the logic here is that all new notes are created without any tags by default, so the app won't add it to the selection / list that you're already viewing, so has to open a new window over the top. So the workaround for me for now is to always try to create new notes in the Notebook view. I agree it is frustrating though - would be lovely to see a fix for it!