I think Sue de Nim is really good. I think Suede Nim has the potential to get mispronounced, which isn't a good thing. Sue Denim could have the same problem, but probably not as bad.
Denim is cool! Have never been able to sew with it though, never sits right. Using solely Denim could limit your costuming a little bit, but then again I dont have a great amount of imagination when it comes to sewing so Im sure there are a million things you could do with it!