I am writing a submission to my acting group's newsletter. 

I would to discuss how films, as communication mediums illustrate
contemporary ethical issues. I think the Matrix & the Truman Show are
perfect examples.
To tie my newsletter submission back to one of the four main ethical
theories (utilitarianism, contractarianism - hobbes or Kant or ethical
rationalism), I would like to know which offers the most relevant and
adequate analysis of the ethical issues that arise in these films.

Actually Socrates (who is viewed as the mouth of plato) abhored
playwrights and artists.
Since he views the world we see as unreal, and compares it to a shadow
he surmises that artists are creating shadows of a shadow. Art is the
shadow of the world we live in, and the world we live in is the shadow
of the transcendent and ultimately "real" world. I'm pretty sure I
recall that being said in the Apology...

As an answer to your question: I would suggest you read Kant's
Metaphysic of Morals. (there is also an abbreviated version: the
groundwork of the metaphysic of morals, which weighs in at about 100
pages, and should pose you no real difficulty).
For both characters in question: the justification for the truth is
more important than the truth itself. While it may be socially
beneficial for people to be oblivious to the matrix, or for truman to
stay; they don't measure ethical action as it's cause of doing good,
but rather their individual wills.

Seriously read the book: there are no quick answers in philosophy
without first reading the ideas of others and then interpretting them
for yourself
cheers