I actually think my friend likes the Pogo Sketch Pro
(that web site looks the most familiar of all). The PSP (note that familiar acronym!) is friendlier to the eye and, importantly, could be used more quickly for day to day tasks than a stylus with a disc.
But if it were me, I'd go with the more anal of the three styli and choose the Adonit. Reviewers and users both seem to say it's the best for writing and I happen to hate imprecision. The Adonit isn't as good for casual tapping on apps and so forth, but everyone says it renders their handwriting more perfectly than any other stylus.