if you've got the money, go with the macbook pro.
If he has the money, he should go for a Macbook and a 23" or even a 30" ACD at home as his auxiliary display monitor instead. Alternatively he can just buy the monitor, a Macbook Pro, and a separate Mac Pro.
For varying amounts of "If you've got the money" you can get infinitely many options, but for his needs the Macbook Pro has absolutely nothing that would benefit him.
GPU? Photoshop doesn't need it.
Increased screen size? Poor colour gamut, graininess, poor colour saturation negates it.
Firewire 800? Who needs that for editing photos anyway?