On my Pearl (MCX)/ Gretsch (Brass Hammered) set, I have Die cast on my snare and my toms.
I find the rim shots on all the drums are brighter. The tuning with the Die-Cast, I believe to be easier because the rims are stiffer.
It is because of a stiffer/ larger moment of inertia.
The "S" hoops and the older Slingerland "Stick-Savers" are also a stiffer rim, but not due to more material but because of the design geometry.
An "I" beam has a higher moment of inertia than an angle of the same weight and is stiffer in most directions.
The change in Die cast hoops and flange hoops is the same as to what happened in bicycles. Of course, Gretsch has been using die casts for a long time. In bicycles the tube diameter used to be 1.25" and made of steel. I hope I am not the only one that remembers bicycles made out of steel. Some bicycle companies starting using an enlarged 1.75" diameter and made of aluminum.
Aluminum is a lighter metal, but it is also not as strong. Aluminum is about 1/3 the ability to resist bending. But, to make up for that, they increased the geometry, made the section larger, the moment of inertia greater, and that made the aluminum frame able to resist bending better. It was still able to do all, that while keeping the weight lighter. Just by playing with the geometry.
The die cast rims are the same thing to the flange hoops and the "S" rims/ Slingerland Stick saver.
Trusses use this trick. Trusses that are used in a building roof and floor supports are very light and can hold an enormous amount of load for their weight.
Ok, I hope I did not put everyone to sleep there. I know I can get long winded at times.