I'm just SLF, but an avid flight simmer, and PSS' Airbus Pro Series (which includes A319/320/321) is generally considered by the enthusiast crowd as the most accurate Airbus for flight sim.
A review:
http://www.avsim.com/pages/0402/pss_airbuspro/pss.html
The web site:
http://www.phoenix-simulation.co.uk/