In truth, there is only one "Retze." The variations would appear to be a Reform liturgical variation from service to service in the Gates of Prayer as are the English translations which are really a matter of convenience as well as a way to make the services more interesting from week to week. The new Mishkan T'filah, I believe, does away with this confusion. I do not believe there are any "rules" regarding which one you might use.
Check out http://www.us-israel.org/jsource/Judaism/amidah.html for some interesting insights into the Amidah.
Jim 230+
An explanation to some questions about the Retze might be found in Gates of Understanding page 207, No. 250, for page 155 of GOP. Other notes are found about Retze for appropriate pages. Philip
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