You can't compare your old side steps to sliders, with one exception that there are a few companies that make sliders with steps or nerf bars sticking out from the side of the truck.
Do you do alot of rock trails or rock climbing, if so slider are a far better way to go?
Just put the Atlantic British Rock Sliders on my 87 RRC after denting the door on a nice rock. They bolt to both the frame and the body and have a couple hole slots to use with a high-jack. Haven't had the chance to test them on the rocks yet, but will post if there are any problems.
After speaking with some local LR rock crawlers when I was shopping for sliders, I got mixed reviews. Apparently if you plan on dropping the truck down real hard on the rocks (not just sliding over them), Rovertym's rock sliders welded to the frame are supposed to be very well made and a better option than the Atlantic British. The caveat there is that the Rovertym sliders have a step section that sticks out and can be pinned upward in certain situations. These are also more expensive than the AB sliders and do not bolt to the frame out of the box.
Stay away from the Safari Guard sliders, they are pure junk, made from too thin of material. I have seen 2 Discos that the drivers couldn't open their doors well because the slider were bent up into the door area.
Go take a look at Rovertym or some who makes some strong sliders, otherwise you might as well put some side steps on and watch them fail.