If he's going to be rendering videos with Premiere, then yes he "needs" a dedicated GPU. It can cut render times by a factor of 4 or more.
If he's just going to be doing Photoshop, a dedicated GPU will speed up some functions (mostly filters and transforms). But overall I don't think I'd consider it "needed". Most of these filters finish in a few seconds or fractions of a second in software.
Some old benchmarks:
http://www.pugetsystems.com/labs/articles/Adobe-Premiere-Pro-CS6-GPU-Acceleration-162/
http://www.pugetsystems.com/labs/articles/Adobe-Photoshop-CS6-GPU-Acceleration-161/
The Macbook Pro recommendation is a good one for graphics design. Regardless of whether you love or hate Macs, Apple loads them with a calibrated screen that covers 100% of the sRGB color space. sRGB is what digital cameras and the web targets, so a screen that displays 100% of it is essential if you want to make content for the web. There are a few PC laptops which can cover sRGB after calibration, and many external monitors do as well. But unless you're going to buy extra color calibration equipment, it's just a lot easier to pay the extra for a Macbook Pro. (Only the Pros; the Airs have some of the worst screens out there when it comes to color rendition.)
Edit: If you must get a PC laptop, the Dell XPS 15 is a good alternative when it comes to color rendition and dedicated GPU. You should probably borrow someone's colorimeter to do an initial screen calibration though.