Difference between "inspiring" and "inspirational"

One difference is that inspiring always means that someone is actually inspired by it, whereas inspirational can also be used in compounds where it means only that something is intended to inspire; an inspirational speaker (or "motivational speaker"), for example, is someone whose job is to give speeches that are intended to inspire, without regard for whether they succeed (so "boring inspirational speaker" is not a contradiction in terms), and similarly, an inspirational poster (or "motivational poster") is a poster that is (supposedly) intended to inspire positive qualities, but I don't think it generally succeeds. But this use is non-predicative; in "the speaker was inspirational" (predicate adjective) or "a very inspirational poster" (modified by very), that meaning is not available, so in these cases inspirational just means inspiring.

"Inspirational" shows intent; "Inspiring" shows effect. So, "Inspirational" often carries an ironic comment on the pretensions of the subject. It is often hyperbole. "Inspiring" is a clean and simple word meaning to be filled with breath which suggests that there was something "breathtaking" about the subjects action. I chose "inspiring" in all uses, except the ironic.

Having noticed that the word "Inspiring" has recently taken a back seat to "Inspirational", I decided to look up and see for myself what the differences between the two words might be. For instance, Kate Middleton referred to Diana as "Inspirational." I thought to myself, "Surely she was inspiring rather than "inspirational". So, I chalked that up to nerves. However, I've since noticed that nothing is "inspiring" anymore. It's always "inspirational". Very strange.