I need to geocode, i.e. translate street address to latitude,longitude for ~8,000 street addresses. I am using both Yahoo and Google geocoding engines at http://www.gpsvisualizer.com/geocoder/, and found out that for a large number of addresses those engines (one of them or both) either could not perform geocoding (i.e.return latitude=0,longitude=0), or return the wrong coordinates (incl. cases when Yahoo and Google give different results).

What is the best way to handle this problem? Which engine is (usually) more accurate? I would appreciate any thoughts, suggestions, ideas from people who had previous experience with this kind of task.