Wavy walls with Ultimaker Cura
I've printed a 2x2x2 cm test cube with Slic3r (left) and Ultimaker Cura (right) and my Prusa i3 derivative machine with tight belts. The print settings should be quite equal (0.15 mm layer height, 40 mm/s outer wall speed, default accelerations/jerks). Though the top surface of the Ultimaker Cura-cube looks much better than the Slic3r-cube,
the latter has much flatter vertical walls than the first.
The front wall of the Ultimaker Cura-cube was printed from left to right which could explain the wavy result as some kind of vibration caused by the sharp y-stop at the left front corner.
But what setting could have influenced this? Should I try to manual setting of lower accelerations in Ultimaker Cura?
Looking at your last photo the cura print on the right. I see the waves on the top side of the cube to the right. This makes me think your infill/perimeter overlap is set too high. I use slic3r so 5% is my perfect number, but I don't know Cura well enough to find that setting. Lookup the infill/perimeter overlap equivalent setting in Cura and try to reduce that number and prevent the nozzle from overlapping too far to the walls.
I don't think that the waves are caused by infills because a) they are too small and b) they do not stretch across the complete vertical shell, but only at one side - always after the corner.
This defect that you see is called "Ringing" and is described in detail here.
In summary, these waves are seen when the print head makes a sudden change in direction in combination with high speeds and high accelerations. As the waves dampen in amplitude the further you get from the sharp corner, this is related to print settings rather than vibrations transmitted through the belts.
Apparently, the settings for Ultimaker Cura differ from the settings in Slic3r, there is no other explanation as the hardware is exactly the same. Reducing print speed and acceleration in Ultimaker Cura will reduce the ringing defects.