: Most art will remain vector. Some things like multiple nested clipping paths are painful to do. See example 1 for just one thing that would be hard to do in Photoshop, not to mention how

Most art will remain vector. Some things like multiple nested clipping paths are painful to do. See example 1 for just one thing that would be hard to do in Photoshop, not to mention how would you edit this in PS?

Example 1: This is trivial to do and edit in illustrator but not so easy in PS.

The biggest problem is that you need to come up with a completely different way of thinking when using Illustrator. So if you just think in terms of how you do things in Photoshop then stay in Photoshop. Being able to think differently helps you as a designer though.

OTOH you can use Photoshop to simulate diffusion of heat :)

Anyway is a very quick list of things that I find useful:

Multiple resolution of raster images
Multiple fills on strokes
Strokes:

Multiple strokes on path
Nonuniform curves (brushes)
Pattern curves
Hard miters
resolution independent strokes
Blob strokes
Arrowheads

Path editing

Rounding corners
Path simplification
Path blending
Expand:

Compound paths
Strokes and fills

Edit vector art with painting tools
Boolean operations on paths
Shape builder
In general nearly all tools work on vector data

Typography

Tabs
Text on path
Multiple colors and effects per character
Multiple transforms per character
Text frames much like InDesign. Linked frames etc
expand text to vectors

More options of merging slicing paths
Auto-trace with colored results, finding center of lines etc
gradient meshes
Modify vector data with live effects
vector patterns
Editing

Live align and snapping
Custom guides
Select by classifiers
Global color
Spot colors

Colored shape libraries.
Artboards (Photoshop has added this)