Questions:
1) What kind of printer are you printing the item with? Specs?
2) What are the print settings?
3) What does the rest of the print look like? What were the differences between the Kisslicer/Slic3r settings?
Just looking at the cube, the upper left portion has tighter lines than the middle and bottom right. As you've pointed out, the gaps alternate.
Others have noted: possibly insufficient flow/width.
This could be due to wobble on your setup, which means there is some tilt/shift when moving in one direction, but not in another, sufficient to create the alternating gaps. Though that doesn't explain the lack of material, which could be a sign of insufficient extrusion.
Minor differences between how pathing is done between Kisslicer and Slic3r could mask the underlying config/build issues better, but since the later under the top layer also shows gaps, I'm thinking it's most likely as others have suggested: insufficient flow or width. There could be a bias in the build of the printer.
W.