I hate to take the Midwestern and mom-like position of "You're both right!" However...
Selfe's argument is well-thought out and compelling. In Eng. 501, we just read about some of the English department's history in the university, and as a Communication Studies major, it saddens me that most of my classmates have never had the joy (and terror and apprehension) of taking a class in public address. I found that the best speeches I gave started extemporaneously, with me just talking to myself, leaving the writing process until dead-last. While my background in learning how to formulate a written argument played a role, the students who struggled the most in public speaking are those who don't adapt their content to their presentation's form. It's true that aurality has taken a backseat to writing, and students (including us current grad students) may be handicapped for that. Learning about as many different modes of communication as possible would serve to enrich our students' lives - along with giving them tangible, real-world composing skills that all sorts of companies would love to have.
However, Hesse also makes a good point. What Selfe is calling for is a drastic re-thinking of composition. While this new definition might fly within English departments and Rhetoric and Composition, it would be necessary to sell this idea to not only other departments, but the administration and students as well. It certainly runs the risk of being seen as taking away from the "serious" work of writing. Another point on which I agree with Hesse is his questioning of just how much composing (not just writing, but creating videos, web pages, sound clips, etc.) students are actually doing outside the classroom. Personally, and before this class, I had a Twitter, Blogger, and Facebook account, and in all three I spent much more time consuming than composing. Sure, I tweeted and blogged every once in a while, and commented or changed my status once a day - but I wouldn't say that I (or most people I know of) are really utilizing all these modes. Perhaps Selfe might respond by saying that is all the more opportunity to teach these kids how to engage more fully in their world - a point I'd be inclined to agree with.
In the end, I side more with Selfe, but I like the cautionary approach of Hesse. He brings up practical problems that would need to be addressed for these changes to be implemented fully, things that can be easy to ignore when caught up in the frenzy of academic theory.