The stock shackles force the spring eye to travel in an arc when the springs compress and extend, which changes the suspension geometry as the height of rear eye changes relative to the front. The shackles also allow for more side to side movement because of the bushings and the lever arm. And the bushings have more resistance to movement.
The sliders keep everything moving in-line, reduce side to side flex and roll with much less friction. It’s not a night and day kind of change, but they’re more efficient and tighten things up at the same time.
Thanks, I appreciate the compliment but I dunno how nice they are. They’re definitely not pretty. They do get the job done and are plenty strong enough. I’d do it a little differently if I was gonna do it again.