Evernote is free, but there's also a premium version available that costs $5 per month or $45 per year. It has a variety of features not available in the free version, including searching inside PDFs and attachments to your notes, as well as a monthly note capacity of 1GB (the free version allows you 60MB per month).
Although Evernote and OneNote are both note-taking tools, they actually have very different emphases and can be used for quite different purposes.
If you're primarily looking for a tool that lets you easily capture, organize and find content from the Web, you'll clearly want Evernote, because its tools for doing that are exemplary. If you instead want to create notes from scratch and have them in well-organized notebooks, clearly OneNote is the way to go.
Then again, you may be like me. I've been using both of them for years. OneNote is my go-to tool for organizing and taking notes for projects such as books and articles. I use Evernote for research. Given that they're now both free, it gives me the best of both worlds.
Sign up for CIO Asia eNewsletters.