My knowledge of graphic design is limited at best, but I love to dabble on Illustrator, mainly doing posters. From the get go I chose Illustrator because someone said you should always use it for poster design because it uses vector graphics.
Now I understand that, but ever since I have encountered examples of people using Photoshop for poster design and using techniques that (to my knowledge) can't be achieved in Illustrator (Mainly the use of photos).
So my question is, how can people use Photoshop for poster art and other printed stuff? On the other hand can something like this (picture below) be achieved in Illustrator?