For me, the form factor is the thing. It seems a little extreme to sit in a Gospel Doctrine class with a laptop computer on my lap. But an iPad isn't as awkward. Of course, you'll get more power out of a Macbook Air and, dollar for dollar, it might be a better deal although it costs more overall. (It may cost twice what an iPad costs but has more than twice the power, storage, etc.) But is it overkill for what you want to do? You could always get a bluetooth keyboard for an iPad if typing is the only concern about the iPad's limitations. And you could put the keyboard away during Gospel Doctrine. (I use the same bluetooth keyboard Apple sells for their desktop computers but you can also get keyboards that are integrated into a nice case for the iPad.)
My real name is Greg Anderson.