I'm Prawn's maintainer and I think the "fine control over rendering at the cost of having to finely control your renderer" is spot-on.

We are working on a long term solution to that problem by finally focusing on building an extension and components layer for Prawn, which would hopefully allow all sorts of other gems to fill in these gaps. But it's a ways off into the future.

If going to Asciidoc is an option, Asciidoctor is now Prawn based for PDF output, and might make sense for simple reports:

http://asciidoctor.org/