Markdown has always looked limited and incomplete to me.
But I can't decide between ReST(+Sphinx) and AsciiDoc(+?) - ReST seems to me like it was better thought out, but somehow my AsciiDoc documents turn out looking better, even though I like ReST more.
Note that this article compares Pandoc Markdown to ReST; Pandoc adds a lot of features that vanilla Markdown lacks.
Of course, this is one of the big problems with Markdown; there are a bunch of different implementations, each of which adds its own extensions. Actually, if you take a look at the Pandoc homepage, you'll see that it implements 5 different Markdown flavors: http://johnmacfarlane.net/pandoc/
"Incomplete" depends on the application. Markdown is intentionally a small and simple language, so it's fine for e.g. comments, but too limited for e.g. a full documentation.
(and as a result, it's tended up to spring numerous incompatible extensions e.g. TFA talks about Pandoc Markdown which adds tables, footnotes and a bunch of other stuff, not "Original" Markdown).
> somehow my AsciiDoc documents turn out looking better
Maybe it's just the default style of the Asciidoc HTML renderer, something like that?
But I can't decide between ReST(+Sphinx) and AsciiDoc(+?) - ReST seems to me like it was better thought out, but somehow my AsciiDoc documents turn out looking better, even though I like ReST more.