markdeck can create diagrams and charts on-the-fly (graphviz, ditaa, plantuml, a2s, Vega-lite).
And it can export the slides as PDF or as standalone HTML file.
Plus out-of-the-box auto-reloading the slides on change, emojis, font-awesome, math-jax, and some other stuff helpful when authoring slides...
But when you don't need any of the above, then markdeck in fact has no advantage over plain reveal.js and markdown.
But when you don't need any of the above, then markdeck in fact has no advantage over plain reveal.js and markdown.