The Hellwig bar helps to stabilize the whole rear-end of the truck. The bar itself is bolted to the rear axle, then the end-links are bolted to the frame of the truck. The end-links have polyurethane bushings at each end that allow for some flexibility. With this configuration, the truck is much more stable. One example is when applying the brakes hard, the truck wants to nose-dive as weight is shifted forward and the rear wants to lift. With the anti-sway bar connected, it prevents the rear end from lifting. Instead, the whole truck tends to squat down. Cornering is improved also. The truck remains much "flatter" (side-to-side) in the corners, in other words, less body roll. These factors lead to a more stable towing experience.
Regarding the Unichip, I installed it within two weeks of the JBA's so I cannot provide feedback on it alone with regards to towing. However, immediately I noticed the shifting and throttle response is much 'crisper' and it would hold a gear longer, before shifting, especially if you're on the throttle merging into freeway traffic. Combined with the JBA's I am very happy!
I'm personally not familiar with the Equalizer hitch, so you might want to check out their web page for more info:
http://www.equalizerhitch.com/