It's not lazy and trite. Just because it's simple doesn't mean it's either of those things. The reality is just that simple: Tablets vs PCs really illustrate core competencies in "Lean Back" (consumption) computing and "Lean Forward" (creation) computing, respectively.
The best analogy I've heard is vehicles. Trucks for heavy duty hauling, cars for ease and efficiency. Because of their form factors and feature differences, the utility of each vehicle is unique from the other.
It's almost obvious, if you think about it. Simple, really.
It's trite because it's inevitable that in a discussion about iPads someone will say it and lazy because just a few minutes using your search engine of preference will illustrate that work can easily be accomplished on an iPad, not because it's simple. In fact there should be a Godwin like law around it. Your analogy is a good one though.
The best analogy I've heard is vehicles. Trucks for heavy duty hauling, cars for ease and efficiency. Because of their form factors and feature differences, the utility of each vehicle is unique from the other.
It's almost obvious, if you think about it. Simple, really.