When using photoshop you have to remember that it is much different than illustrator in many ways. You can only undo once, you must always select a layer, and you have to change the opacity and light settings. But they have their own similarities too. They both have multiple layers that you get to use at once, and you can be very creative with both. Photoshop could be used with illustrator too because, you could create a new design in illustrator, and then edit it to your liking using photoshop. Photoshop is a great tool to use when editing pictures and designs. Illustrator is great for making those designs & for creating new ones.  

I like using illustrator better than photoshop because, photoshop is very difficult to use and to learn. Illustrator is easy to learn, and fast & fun!