Your salesman was mistaken. The main sway control on the Equal-i-zer 4 point hitch comes from the friction between the two sockets where the bars insert into the hitch head and the upper metal portion of the hitch head. The amount of pressure on that surface when the bars are tensioned is tremendous. This is what they are talking about when they say "rotational sway control". They count each bars socket as one point of tension each.
The secondary points of sway control (3-4 of the 4 point) is the contact surface of the WD bars on the flat portion of the L brackets. There is one on each side of the A frame so they are counted as one point of tension each - hence the advertising claim of 4 way sway control.
The amount of steel on steel pressure is MUCH greater at the hitch head compared with the pressure on the L brackets so most of the sway control comes from this area.
Hope this helps understand it a bit. :)
Regarding the Dual Cam system - The big advantage to that one is that the tension increases the more the trailer tries to swing. Also, the Dual Cam does not restrict the trailer from returning back to center like the Equal-i-zer does. The Equal-i-zer tries to hold the trailer in position no matter what angle it is at. That means that the same amount of sway control tries to keep the trailer "turned" as it did when going straight. This is in contrast to the Dual Cam which assists the trailer in straightening up after a turn or sway event.
One big advantage to the Equal-i-zer is it's ease of installation and adjustment. The Dual Cam can be quite difficult is some cases to get installed and adjusted. It take much more time but the effort is usually well worth the time. I towed for years with the Dual Cam system and that is what I would go with again if I were you, especially since you are familiar with the hitch.
Barney