From the looks of some of those cages there some to stiffen up the body of the car for what ever type of racing they do and some meet the DOT crash safety stuff too, for that SERIOUS all out racer. Its kinda like having a 2 piston big brake kit and a 6 piston brake kit. Both are bigger but both serve different purposes for different applications.
LOL...WHAT?!?!
News Flash: Cusco cages, bars, and other show bars and cages are not race legal, they do not strengthen anything.