NoMa is very block by block. While it is by and large safe, it can feel sketchy in spots, especially in the areas near the public housing developments. I've heard it was way, way sketchier in the past. That said, you can save $100 to $200 a month living in NoMa, though, as the rents are typically lower there..

Wharf is cool but it's also expensive and not nearly as close to the Metro as you think it is unless you live directly by the Metro station at Waterfront. I like visiting the Wharf every now and then, but in general I could never see myself living there.

I personally live in Gallery Place/Chinatown and love it here. Sure the apartment buildings in the are older but the area is far more convenient to transit. If you take Amtrak often, you will surely appreciate the proximity to Union Station. I recommend Gallery Place/Chinatown out of the three for sure.

I am personally not bothered by the noise in Chinatown... If noise is a concern, NoMa is a better bet.