While I think that Marx himself might not have fully envisioned the power of literature when it is geared towards social contexts, I think that the Marxist school of literary criticism might be a way for you to examine both works.  In this line of thought, literature is examined in how it presents the relationship between those who own the means of production and those who do not.  I think that the Marxist literary critic would focus on how Dickens and Hugo present the disenfranchised of an order that predicates power being given to those who own the means of production.  Dickens and Hugo spend considerable time in both works addressing the issues of what the Marxist critic would see as "the proletariat."  The mass rising in Hugo, speaking the need of being able to possess autonomy in determining their own future, and the focus of Dickens on the plight of those suffering under "Poor Laws" and other forms of legislation that benefit those who own the means of production would be of importance to the literary critic.  I think that the Marxist literary criticism line of logic might be able to yield some interesting points in comparing both works by Hugo and Dickens.