iPads can be a bit more ergonomic than Cintiqs, but if you can deal with the pen-screen disconnect then classic non-screen tablets are significantly more ergonomic than either, on top of being significantly cheaper. YMMV though, some people need that pen-screen connection.
The iPad/Pencil combo knocks it into a cocked hat.
The kicker is that the Cintiq is around the same price (or more), and is less ergonomic.