The slat wall is the best design. Each of those steel tubes is filled with concrete and ramming a 10 ton truck into it will not move it. This design has been tested by the military and the Border Patrol and deemed the best. I believe the slats also go 10 feet under the ground. Then there's other classified stuff we don't know about.
Great report on that Mother of Walls. Israel has a fine secret recipe or two that may have been taken into consideration.
With Serious people in charge, Tunnel digging should be a NON-problem, in this Age of intelligence. The Dark side did nothing to stop tunnels, but open their jaw a little for the cameras, when discovered. Why do I have a feeling tunnels were largely ignored. That Trust thing again keeps gnawing. .
How are they for scaling, compared to a concrete wall? I could see young Mexicans using the gaps to move themselves up and over. But I haven’t seen any testing of that.
You are ignoring how easy it would be to design a tool to wedge into the slats for climbing them. Shoot—low tech is probably doable with a knife & some wood.