Here's a handy cross reference for Harley plugs.
Be advised that a change to a different plug or plug wire than stock could result in setting a code in the Delphi systems of later year Harley's from the ION sensing system that uses a set resistance to detect knock in the engine.

This is not usually true if just going to a colder heat range.

Usually a change between the HD plug and Champion plugs will set no codes.

Also here's a handy reference for all plugs in different bikes.
Spark Plug Interchange Guide (http://www.nightrider.com/biketech/hdsparkplugs01.htm)

http://i149.photobucket.com/albums/s45/bills985/SparkplugXref.gif

Is there one plug better than another?

I would use the stock plug because of the ION sensing. If you change to a different type plug the ION sensing system will not work properly and pinging/detonation will not be detected and dealt with through the resistance in the plugs.