With medulla seems to be much smoother and brighter, which makes sense as it was said in the previous slide that the medulla scatters light. At the same time, I could believe that either picture is "real hair" though. Is the strength/width of the medulla dependent on person/species?

Yea, both of the "hairs" seem rather flat, dry, and bundled, not really resembling actual human hair. Maybe increasing the percentage more would help to make it more realistic?

The hair in the first image is obviously a bit darker, and in my opinion, that's the more realistic looking hair because it seems smoother and softer, like actual human hair. The image on the left is reminiscent of the hair of like a Barbie or something, semi-realistic, but rougher and frizzier than most human hair. I actually think I disagree with the followup above me because I feel like adding more medulla might make the hair look less realistic