Hello Tav,
I happen to know these other tools really well, but there is not that much Inkscape can do that the others cannot. That said,.. these are the most important aspect why I started to use Inkscape almost exclusively.
** Some other things Inkscape does that the others do not.
*** Inkscape uses SVG as it's native file format. This ensures a minimum of fuss in publishing documents on-line. It has the single widest support of the SVG 1.1. standard of all authoring tools you may find.
Some of the tools in Inkscape are without equal. The filter editor allows you to create effects that other tools cannot hope to accomplish simply because their native file format is not SVG. There are always conversion steps you have in other authoring applications that you will not have using Inkscape. Errors therefore are confined to browser or viewer implementation.
Though some of the basic functions in Inkscape are a bit Spartan, it often is at the more complex things you can do with vector graphic that Inkscape can do things nothing else can out of the box.
No other authoring tool will allow for editing the code directly, through an XML editor, nor does any other authoring tool allow you to add scripts in your SVG code, both in Inkscape and outside it, which will be negated by the editor and left alone during the parsing of the drawing.
You can often take arbitrary code generated by other authoring applications or even hand coded SVG and happily edit the file in Inkscape and save it back without it being messed up by the editor. Very few other applications are as forgiving accepting drawings from other applications and then being able to edit them.