I have the same car (2009 jetta tdi, black on black) and I am using what many here seem to suggest, which is woolite (high efficiency) diluted 4:1. It seems to do a good job cleaning the dirt off, though I keep my car really clean.
I don't use 303 because I fear it would rub off on my shirt and pants. 303 is pretty greasy. It does a great job, but I wouldn't use it on something I was going to touch regularly.