I don't like pencils, for my vision the color is too low contrast with the paper compared to black ink, or even blue ink, and for that reason I prefer a .7 nib to a .5, the thin lines also result in less contrast (they also make a scraping "sound/sensation" on the paper). but I didn't comment just to say that, but I selected your comment as a representative sample for a broader comment:

hey everybody, could you tell us why you like something rather than just that you like it? We had a mechanical pencil recommended, and then two more mechanical pencils recommended, but I'd have to do my own research to figure out why I would choose one over another. Whereas, you all already know what I'm looking for in a writing implement (high contrast and maximum smoothness)

even though I don't think I want a pencil, I do have opinions about mechanical pencils, for example I love when they can autofeed new leads.

I like the rOtring 800 because it's heavy in my hand but the actual lead-on-paper "feel" is extremely smooth. Contrast depends entirely on the lead you put into the pencil. For max contrast there are versions of the 800 with thicker tips, (iirc) even going up to the regular pencil nibs that you can sharpen (if you know what I'm talking about, I don't really know how to properly explain it).

Basically, I like it because it's a high quality writing utensil that I won't get worried about.

A lot of people don't like the 800 because of the retractable tip, but as someone who has this pencil in their backpack all the time (and who has had the non-retractable version unfortunately ruined in a backpack) it is an absolute necessity.