Is there any benefit from choosing a god? What are they? Do they change per level? Is it available to use at all times? Do they involve rituals? What are the prerequisites?
In 4th ed, the only real mechanical differences you get from following a specific god are that it determines the types of Channel Divinity powers available to a Divine character, and perhaps allows some additional feats, paragon paths or backgrounds.
Also, note that a Warpriest, an Essentials cleric, gets different powers based on the type of god (domain) he follows although again, this is tied more to an ideal than a specific god.
Mechanically there are no benefits. Gods and alignment play little to no mechanical role in D&D 4th edition.
Clerics can worship any god or none. Divine classes such as Clerics and Paladins have access to the same powers regardless of what god they worship or alignment they belong to. From a cursory inspection I cannot even find paragon paths or powers restricted to followers of specific gods: even a worshiper of the Raven Queen can use Pelor's Radiance.
Off the top of my head the only thing I can think of which actually cares about your god is artifacts, which can be aligned to specific gods and favour worshipers of their gods or members of that god's alignment.