The most convincing black I've seen is on Bergger Silver Supreme, a matte paper with a "velvety" surface. The Dmax is far lower than from a glossy RC paper, yet the shadows look a lot deeper.
I also find that warmtone papers tend to give better definition in the shadow areas, despite their much lower Dmax.
So in my opinion, Dmax is overrated as a "quality index" for printing papers. I'd almost say "utterly useless", but I think I will antagonise enough people without going that far