The best way to explain the functionality and advantage of Evernote tabs is to compare them to browser tabs, which replaced opening multiple windows. Reducing clutter is an important part of my workflow. I have mimicked the effect of switching between different notebooks in the Evernote sidebar, and it is not the same as switching between tabs. Right now, I have tabs open in Evernote Legacy, and the efficiency is MUCH better than the new version. I simply cannot quit Evernote Legacy until it is permanently removed.