I've wheeled the hell out of the GM units. They fit nice and tight against the truck, which is my preference (they don't hinder your calf getting in or out). I have jacked both wheels off the ground by using a Hi-Lift on the rails, with zero issues. And I actually supported the truck in the air for a six-month project by using the GM rails. So they are more than adequate. I also have the removable steps...a nice feature that other rails don't offer.
On the downside...because they hug the body so tightly, they don't have the side protection that the others have. Then again...you don't have to step over them every time you get in or out. All depends on what you're looking for, and how crazy you get. It also has alot to do with the terrain you wheel in. Here in the midwest...trees are more of a concern than rocks, and the rails keep the sides and top corners of your cab off the trees.