Pick a steel. See its typical hardness, how long the edge lasts, and which abrasive will actually sharpen it.
What decides your abrasive is not hardness, it is carbide content. Vanadium carbides run around 2800 on the Vickers scale while aluminum oxide stone grit sits near 2000. When a steel carries lots of vanadium carbide, ordinary stones plow around the carbides instead of cutting them, and the edge never gets truly crisp. Diamond at 10000 Vickers, or CBN, cuts everything.
Simple carbon steels and basic stainless sharpen beautifully on any stone. Mid tier powder steels like S30V work on quality waterstones but reward diamonds. Past roughly 4 percent vanadium, diamond stops being a nice to have and becomes the requirement.