:3 I'm in love with Illustrator.
You are correct in that you can use either of these to create artwork. But you need to realize one thing:
Photoshop and Illustrator are based on entirely different principles.
Photoshop is a raster-based (pixels) photomanipulation program at its core. It can be used to create beautiful works of art, yet, but that's not what it was originally made for. With Photoshop, you are confined to the size and resolution you begin creating at - if you enlarge something that was done in Photoshop, it will become blurry and pixelated.
Illustrator is a vector-based (shapes & mathematic equations) drawing software. It is used for advertising, typesetting, etc. The incredibly awesome thing about creating artwork in Illustrator or other vector programs is that you can draw something the size of a postage stamp, enlarge it to the size of a house and it will still have the exact same image quality.
To show you the difference between the two, here's some pictures to show what I mean:
Photoshop images:
(Note that the image on the left is 100%, the image on the right is about 300% magnification)
Illustrator images:
(I don't seem to have any of my finished Illustrator files on my laptop, as I move them all to storage or my PC, but here's a bit of a WIP so you can see kind of what I mean - the hair/headband is all that's been vectored.)
(Notice how the image on the left is 100%, and the image on the right is 1200%, and there is no difference in the appearance of the vectored art.)
On a final note, don't use Illustrator if you dislike the Pen Tool from Photoshop. XD You will use the Pen Tool for nearly everything in Illustrator.