and use a decently specified laptop. It will be every bit as good as a desktop in terms of performance, and although it will cost more initially he might soon be glad he went down that route when he doesn't have to lug a box plus keyboard etc around.
I regularly work with large graphic files, and PowerPoint presentations and my laptop handles it all perfectly. When I want a bigger display I simply connect the machine to one of my monitors.
The great benefit of the laptop is that I can take it wherever I go, and no matter how much you try you can't use a small form factor PC on a plane ot train, or in an airport lounge.