As a theoretical physicist, the iPad can handle work-related tasks that the MacBook cannot (and vice versa). The unique iPad features mostly center around the Pencil: annotating papers, and doing "pen-and-paper" math, except that the iPad is far superior to pen and paper (you can move things around and "re-edit" them). Actually, the iPad can handle most things the I generally prefer the MacBook for (programming and writing, mostly), but there's usually some hoops to jump through. But it's certainly good enough that when I travel, I usually only take the iPad.