Well, I don't really listen to music to make me smarter.
You can maybe prove that one type of music stimulates your brain more then another,
but does that make it "better" then the other?
I just don't think it is possible to decide that one type of music is "better" then the other.
Music is not created to make you smarter.
It's created either to sound good/entertain or to make money.
And what exactly makes Mozart's composing any better then anyone elses?
How could you ever judge it scientifically when music isn't a science?
You say you can judge someones composing technique,
but could you describe how?
However you decide to judge it it will be by your standards of what you think music is.

Tupac's music didn't produce the same outstanding effect
Are you sure about this or are pulling facts out of your ass?

The best guitar player in the world sucks if nobody likes his tunes.
So if the greatness of ones music is judge by how many people like it,
Rap and pop would be superior to all other forms of music.