Honestly, either would work just fine. Many colleges are now using the Bew iMacs in their art programs. If you're not doing much more than just that level of work, I'd suggest that one. If you're going to be doing massive projects and dealing with long renders, get the Pro.
Also, while I acknowledge the fact that Apple's stuff is pricey, there are still upsides from this that he wouldn't get from a PC/Hackintosh. A few are:
- Far more optimized than most homemade computers
- Apple aesthetics (and yes, this can be very important to some people)
- Aluminum case
- Improved cooling
- A (mostly) worry free OS pre-installed
- Ease of use with other Apple devices
- Apple-specific technologies
...and many more. I won't deny that he could build something with the same power for less, but the above advantages DO exist, regardless of whether or not the people want them to/think they do. And he's clearly stated many times over that the choice is between these two.