Mildliner: The pencil has two tips at each end: bevel and round (a little wide). The bevel tip is great for highlighting, while the round tip is great for writing titles or sketching.
Clickart: The retractable tip is harder than Mildliners. It round with a size of 0.06 mm. It is perfect for writing (more finely) or drawing small elements, such as stickers icons.
Mildliner: They come in 30 colors. The ink is rather translucent like a highlighter, perfect for writing in black on top. The ink generally does not bleed through most papers.
Clickart: 48 colors. It is a felt ink, opaque. Like Mildliners, the water-based ink does not bleed through the sheets.
In the two types of pencils, the colors are not identical. Clickarts are not based on Mildliners. On the other hand, yes you will find a pale blue which is similar in each collection for example. But as the Clickart have more colors, you will find different shades so as not to make your tone on your equal.