Traditional grammar would suggest that they are the same- s + v + adj + inf.
Tranformational grammar would show that they are very different. By turning them into the passive, we can see that they are different:
It is hard to please him (OK)
It is eager to please him (Not OK)
Henece, transformational grammar looks more deeply at how the sentence really is structured, rather than simply labelling words. ;-)
constituent structure: the relationship between words based on their position in the sentence:
[[TheyNP] [gave us a bookVP]IP].
Traditionalists defined and classified the parts of speech according to their meaning. Structuralits did it on the basis of structural analysis; transformationalist, or generativists, took it to another level. They looked at how speakers used parts of speech to generate sentences.
Today, we use 'form' from traditionalists, 'function' from structuralists, and transformations such as WH-movement from generative grammarians.
"Excuse me, where is the library at?"
"Here at Hahvahd, we never end a sentence with a preposition."
"O.K. Excuse me, where is the library at, @sshole?"