I started with OneNote in 2008 which at the time didn't sync across computers. I figured out how to utilize Mesh Sync (eventually became OneDrive) to sync my notebooks across PCs but often had issues with corruption of Notebooks. Then I found Evernote a month or so later. I still use OneNote as it is required for my job, but personally, I rely on Evernote. There are a lot of ways Evernote could improve to match what OneNote does, but to me, the biggest differentiators which make Evernote stand out is being able to tag notes, the search being FAR SUPERIOR to OneNote and the screen layout which is similar to how I layout Outlook. I cannot emphasize enough how easy it is to find things in Evernote compared to OneNote.
Microsoft will always dominate the enterprise space because business runs on Windows and Office. However, there will always be room for niche products like Evernote that provide particular value or features that Microsoft cannot, particularly in small to mid-size business market, as well as some pockets in the enterprise. As long as Evernote stays a step ahead or has a few must-have features that OneNote doesn't, people will pay for that and they can stay relevant. If they sit back, relax and don't keep up, they will become the next Novell or Lotus Notes.