Totally worth the expense, do a lot more than reducing sway. They are actually an aid in weight distribution, changing total load on hitch to spread it over the tow vehicle. This is where your better vehicle control comes into play.
They make a great difference in any bumper pull combination, use them every trip.
First off, sway bars is a misnomer. There is sway control, then there are Weight Distributing Hitches, and then the premium WDH with sway control built in.
As for whether or not you need them, depends on the truck and trailer. A 2H BP really should not sway, it's almost impossible to load them wrong with the axles at the rear of the trailer. So generally sway control is not necessary. A WDH is another matter, a 1/2 ton (or smaller) probably needs the WDH to distribute the weight and 'stiffen' the vehicle's suspension. A 3/4 ton or larger probably not necessary. A 3H BP (or larger) is where a WDH and sway control really becomes a necessity.
To answer your question;
When I hauled with a Explorer, yes the Equal-i-zer (WDH and sway control) was well worth the money.
Now hauling with a 3500 SRW Duramax, no I don't use it and it's not worth my money.
Nearly all of what I post will be controversial to someone. Believe nothing you read on a chat room, research for yourself and LEARN.
Not in the 42% or the 96%
I've had a trailer sway event occur twice: Full size p/u truck, steel 3H BP with two average QHs on board, in the front two slots.
Headed down a long hill with very steep, grassy banks on both sides, semis coming at me loaded with coal. FUN!!!
Next, leaving Chattanooga TN on 59 South with trucks and 3 lanes of southbound traffic and weeee the trailer's in charge again.
If the trailer tires synch up juuusssst right with the tow vehicle tires, the trailer can take over and create sway. Esp going down hill. I don't CARE that you have trailer brakes. The trailer is pushing the truck.
Now I knew how to fix it...bump only the trailer brakes with the manual deal on your controller. but most folks don't know that. and it was still scary as ****.