A screenshot proves that something existed. A case study explains why it mattered.
What a useful project page answers
What problem existed? What constraints mattered? What did you personally do? What technologies were relevant? What decisions were difficult? What changed because of the work?
Better for humans, better for search
A detailed project page creates natural language around your expertise and gives other pages on the site something valuable to link to. The SEO benefit comes from the usefulness of the page, not from repeating a job title twenty times.