The equalizer hitch is a weight distribution (WD) and an anti-sway hitch in one. It is a good system.
The "Dual Cam High Performance Sway Control" that you reference in the second link is an add-on to a Reese WD hitch. You have to have the WD hitch in order to use the Sway Control. Follow
this link and scroll down to "STRAIT-LINE WEIGHT DISTRIBUTING SQUARE BAR/TRUNNION HITCH SYSTEMS WITH DUAL CAM SWAY SYSTEM".
If the trailer really weighs 4000 lbs, then you probably don't need a WD hitch. That trailer is only 14ft long. I would be surprised if you have any sway issues. You might try posting on
http://www.rv.net/forums in the "Folding Trailers" or the "Towing" sections. You will get advice from others with a similar setup.