I’ll try to explain, even if it’s a bit hard without pointing out things in real time on a video: RDK animates by drawing the frames by hand, on paper, to then scan them and color and edit them digitally, while Sugarcube does everything digitally, working with vectors (in Toon Boom). So Sugarcube outlines are extremely smooth, clean, often with the same thickness all over the frame (look at the difference in the eyes outline)

Meanwhile RDK ones, being hand drawn, on paper, are less smooth, and sometimes you can see where the pen left the sheet



The way the characters are drawn is also quite different, in some scenes, but that’s not always as obvious or apparent. The one below is an extreme example.



That’s probably because Sugarcube animates all episodes by strictly following the proportions of the character sheets, so they look the same in every episode, while RDK seems to adapt the style of the individual episodes to those of the storyboarders who worked on it: some draw the characters with biggers eyes, some with bigger irises, some draw them a bit taller / slimmer, some draw their heads bigger…

Similar pose, very different proportions

As mentioned earlier Sugarcube draws using vectors, so the models can be rescaled indefinitely without loosing quality or details: characters seen in the distance are just smaller versions of the usual models



Meanwhile RDK draws by hand, so obviously small, fast moving details are going to have less details, since there’s a physical (and efficiency) limit to the way one can ink.