Here are some features of Serif Drawplus X8 that I like a lot and never found in Adobe Illustrator:
Easy creation of measurements:
these measurements wil change on the fly when resizing the object.
Right clicking on a ruler gives a contextual menu:
A guides manager to create guides EXACTLY where needed!
Moving the rulers and pulling out some guides while seeing exactly where these guides go:
Easy replicating and spacing of objects:
Interactively creating rounded rectangles while keeping them adjustable afterwards:
Live creation of shadows and adjusting them:
All of these features are very easy to adjust afterwards; not so in Illustrator.
I have been struggling for hours to change the rounding of rectangles in Adobe Illustrator: it was a true crime!