Have you experienced more success showcasing the business value of IT from a storytelling perspective or with specific metrics?

In my experience, both is best. Data provides the facts and trends, narrative the analysis, context and richness. Agree with Stefan, non-financial metrics are also useful to illustrate the breadth of many IT organisations as well as business integration (eg staff completion rates of cyber training).

Metrics are always powerful, but they don't always need to be direct financial metrics (ROI, TCO) - they can be proxy KPIs as proof points that the "story" is real. E.g. % of x events fully automated. It also helps isolate the measure to the IT contribution, whereas financial realization may require broader dependencies (e.g. organizational restructures etc).