I did a simple comparison a year ago showing eleven different geocoding services, free ones as well as pay services, and the results are in a google spreadsheet. I work at SmartyStreets, so you'll see that listed in the first column but not in first place. I tried to make the comparison unbiased so the results are actually useful. I have now opened the comparison chart for editing by anyone. If you can add to it, please do. Keep your edits objective, don't try to spin things.
geocoding comparison chart
The exact location was determined visually by finding the location on googlemaps and dropping a pin there to obtain the lat/lon.