What are the main arguments involved in the Orientalism debate?

I assume that you are asking about arguments in the debate
over Said's book Orientalism.

Said's
major argument is that the West has defined the East in terms that serve to justify the
West's domination of the East.  He argues that the West has defined the East as
effeminate and inferior.

There have been many strands of
criticism of Said's work.  The best summary of these critiques can be found in the
topic/Orientalism link below.  The major criticism, in my mind, is that Said's argument
is as simplistic as the scholarship that he criticizes.  He, for example, criticizes the
West for seeing the East as a homogeneous mass but he himself does not differentiate
between Western views of the Middle East and the Far East.  He lumps those (very
different views) together and calls them all
"orientalism."

Another telling argument is that what Said
criticizes is not really a Western fault.  Instead, it is a fault of all cultures.  All
cultures tend to stereotype one another rather than to see each other's complexities. 
The Arab world, one can argue, stereotypes the West just as much as the West stereotypes
the East.