I have the 4 Plus body-mount sliders. I like them, I have not had to use them as a Hi-Lift point yet, and also I have not had them hit either (and I have tried). When I got mine I couldn't find anybody that made frame-mount sliders and so I compromised. I added a strip of black grip tape on the top of the outside tube to make using them as a step easier. Ever had your foot slip off a wet tube and hit your shin? Good Times. The 4 Plus ones have a thick angle that mounts to the body and it doesn't seem to flex when I climb on them. Oh and one more caveat and YMMV... My rollcage is bolted to the frame tie-ins that sandwich the body tub, so there's a lot less chance for body flex in that area, which may explain why mine don't seem to flex much.
I like the White Knuckle ones however I would definitely get the heavy-duty version, but I would have them modified to have a rear kicker and not be angled like the ones in the pictures. Plus I would seriously consider welding them to the frame.
My All-Pro sliders have been on my 4Runner for years. They are welded to the frame, the rear kicker works great as a pivot point, and work great as a Hi-Lift jack point.