I'm not sure what the Curt and Draw-Tite hitch's actually bolt to (the sheet metal aft of the spare tire?) but I sure wouldn't want to pull a very heavy load with either of them...
The factory hitch has inserts that bolt into the rear pseudo sub-frame rails and is a little more confidence inspiring...
But I'm sure the Curt and Darw-Tite are fine for bike carriers and other light loads.