Evolution has two options for views through "View" → "Preview": the classic view and the vertical view. The classic view is the default now.

The classic view was obviously a good choice for a default in earlier times when widescreen monitors did not exist yet and most monitors used resolutions with a 4:3 aspect ratio.

But now widescreen monitors are practically the only thing you can buy, and they have resolutions with 16:9 and 16:10 aspect ratios. Vertical space is scarce so the vertical view is most efficient for those. That's why I hope Evolution could use the vertical view by default. If I'm correct, Microsoft Outlook 2013 also uses a vertical view by default.

Personally I like the alternative arrangement for the vertical view in the third screenshot the most because I think it's more efficient with space. It occupies just one line instead of the two lines needed for the "Messages" column used by default if the user switches to the vertical view. The third screenshot was taken with display resolution of 1680 by 1050 On even higher resolutions such as 1920 by 1080/1200 pixels this would be even more desirable. Maybe this "alternative vertical view" could be used as default only if Evolution detects a 1680 by 1050 pixels resolution or higher.

Also see bug #692572 for a suggestions on improving the "Messages" column of Evolution's vertical view.