Hi Myles,
Thanks for using syncfusion products.
You can find the similarities and the differences between the two API from the following documentation link.
GridGroupingControl:
http://help.syncfusion.com/ug_94/User%20Interface/Windows%20Forms/Grid/default.htm?turl=Documents%2F434conceptsandfeatures.htmGridDataControl:
http://help.syncfusion.com/ug_94/User%20Interface/WPF/Grid/Documents/42griddatacontrol.htmPlease let us know if you have any queries.
Thanks,
Jawahar.