Comparison adjective (I am the better of the two students.)

Are these two sentences all correct?

I am the better of the two students.
I am the better student of the two.

What are the two comprison objects in following sentence?

He works less hard than I think.

Hi Ninicheng,

Your first two sentences are fine. In your third sentence the comparison is between how hard he actually works and your opinion of how hard he works.