One thing that Illustrator has that Inkscape (or other vector editors) doesn't is the gradient mesh tool. This is sort of hard to wrap your brain around, but can be used to do things that seem impossible with vector software (and more).

You might also be interested in some other threads on this forum about Illustrator:

A portal to vector art
Mercator projection template
Photoshop vs. Illustrator
Vector mapping
More Illustrator vs. Photoshop
Reliable Highlighted Text in Illustrator
Relief shadows on Illustrator
Variable Typemasking in Illustrator
A type of task vector editors are way better at
Vector vs. Raster - when to use which?
Inkscape strategies: coastline, outlines, and borders