I think the purcy is looks exactly the same as the harry one but is only rc4 compatible. The harry is a hybrid one so works with all the systems.
http://www.bbksoftware.com/
http://www.bbkrclive.com/2010/Offroa.../RC4System.pdf
this page has all the info that you would need regarding the differences.
If it was me id get a harry, a bit more expensive but you know it would work everywhere.
