There is also a XF VSF version, 022056. Other than larger unions, the XF series appears to offer no significant performance benefits (contrary to the sell sheets) over the originals so I don't know why they bothered with these either. Other than perhaps to extract more money out of unknowing customers.
When I first looked at the Energy Star data there was little difference between 022055 and 011055. The XF had 1-2 GPM higher for each curve and the wattage was a little higher too. But I just compared the two in the energy cost spreadsheet at exactly the same flow rates and the XF has a little better efficiency (~5%). It just wasn't that obvious at first glance.
But really the difference only save about 10 cents a month @ 50/25 GPM & 1/5 hours per day & $0.10/kwh so it takes forever for the XF to catch up to the VST with just a $100 difference. Well beyond the life span of the pump.