I have the Jeeperman ones that attach to the frame. You cant get them new anymore, people do sell used ones from time to time though. They require no holes to be drilled in the Jeep. I have had the entire weight of my Jeep sit on them, drop on them and used as a pivot point for me to get around a tree stump.
But you can still get the Detours Drop Kick sliders http://www.detoursusa.com/dropkicks.php
They attach the same way and are just as tough.
I will agree that the tub mounted sliders are tougher and stronger. But unless you live in a place that lets you run the hammers or hells gate all the time its really not needed. I have seen a set of the detours get pounded on for 2 years by a guy in our Jeep club and his rockers are still just as straight as a stock Jeep.
But to be honest my main purpose for them was they are a much better step for the (vertically challenged) wife then the tube type rockers. Who informed me when I bought the Jeep that "if I was going to lift this one like the last one, it better have a step on it."