The first one allows you to display a long text in a BOXTEXT objet. The text can be display on sereval lines if needed. Just set the extended type in your ressource editor. Long text is read or written using the function ObjcString().
The second one is an editable object without limitation of text size. This object is very easy to handle and usefull and replaces effiencly the standard EDITABLE object. However, standard EDITABLE object can be used in a case of formated fields (such as date input for example) because XEDIT objects don't use the template string (as G_FTEXT objets).