We take our Class C off-pavement, so we need maximum coach body strength.
No engineering degree is needed - just common sense - to figure out that a slide basically puts a big hole in a wall that has got to weaken it. What a slide does to a wall is reduce it's shear area. Shear strength is watched very carefully - and building codes ensure it - in walls during construction of buildings. We especially went overboard in shear strength on our residence because of earthquake considerations here in CA. We made it through a big one in the late 1980's only 3-4 miles from it's epicenter with no structure damage, due partially to double plywood walls for extra shear strength.
I figure that a motorhome is at times being subjected to earthquakes ... at least when off-pavement (and on Interstates here in CA) ... so we went with no slides for extra margin. :E