there is no difference. This are the same objects. If you are using the WPRichText you probably will use the 'TextCursor'.
Name 'Cursor' was already taken in TWPRichText.
TextCursor is a powerful class which handles the cursor movement, DropMarkers and Selection. It is owned by the TWPDataCollection - this means if you have several TWPRichText working with the same text they will share the 'Cursor'.