I'd like to propose the image that instantly caught my attention (and almost caused me a stroke :P) when I read the chapter: page 9, Erwin remembering the time when he convinced Levi to continue in the Survey Corps after Farlan and Isabel's deaths.
It may not be most illustrative panel about the events of the chapter itself, but it is undoubtedly the most transcendental for the story as a whole, because it is the first time Isayama makes a connection between the main continuity and the events of No Regrets, finally giving us the confirmation that No Regrets is canon. \o/
We might not have another connection between the two mangas again (unless Levi's past is explored for some reason), so if we are going to feature it, this is the time.
Hopefully, as the Corps continue digging into the origins of the Titans, with the secrets of the basement and the mysteries of the Beast Titan, we could get a connection with Before the Fall and confirm if that spin-off is canon as well.