hey X,
each app has it's own set of strengths and weakness. as you are already aware, Illus is a "vector" app and PS is more of a "pixel-based" app with some vector capabilities.

anyone who works in vector will tell you PS is NOT the prog to use if you need complex vector art. it can handle minor shapes and paths but Illust (and apps like Freehand, Fireworks...) handle the math a heck-of-alot better. it really breaks down to the style and type of artwork/illustration needed. i do all my ad-work and illustrations in Illus (unless photo manipulation is required, even then, i use Illustrator to put everything together). i find it handles the "text" better. they both work well together for me that sometimes they act as one app. i just don't see Adobe merging them together anytime soon ;)

:)
retrocity