The thing about Illustrator is that it's specifically for vector images. In fact, it hates raster images and works very poorly with them. Comparing it to CSP is sort of comparing apples and oranges. Though CSP has some vector based options which are extremely helpful, it is still a raster program.
The pen tool in Illustrator is far easier to use than the sorta one in CSP, but I've been using Illustrator for over 10 years and CSP for about one year.
Illustrator will have a learning curve for someone who has used CSP, but it is an incredibly powerful program for what it's for. Though some designers scoff at it and use a different vector-based software, I forget the name off the top of my head since I don't use it.