> [...] and very very verbose

it's possible to write compact SVG. For example, it has a simple and very compact sub-language for specifying paths (with one-letter commands): http://www.w3.org/TR/SVG/paths.html#PathDataBNF

What do you mean by 'not as well supported'? SVG is supported by Firefox, Opera and Webkit (Safari / Chrome). I'm not aware of any Browser that supports Postscript.

As for turing complete: SVG is fully scriptable with Javascript, which is turing complete and built-in in every browser.