To be honest, I am not sure what the neighborhoods are even called. I was mostly escorted around when I was there last. The waterfront area on the river is awesome and probably the most tourist friendly. Raffles hotel is insanely nice, but it's not really Cambodia if you ask me. A place where socialites go to say they visited a third world country.
In general all of the hotels are very nice for the money. Raffles is NYC priced and feels like your in New York inside.