Real Greddy pans have "SR20" cast into the front and the Greddy logo on the bottom. Older ones have the Trust logo on the bottom.
While there are many copies, I am not sure if there are any that also retain the logos. One can also tell the copies apart by the swing baffles. The authentic Greddy ones look nice and precise, while the knockoffs use slabs of steel riveted to some re-drilled hardware store door hinges.
I have a knockoff pan and I removed the swing baffles because I do not trust any moving contraptions in my oil pan.
As for materials, I prefer the cast aluminum because it will just shatter when hit too hard, as opposed to pans that dent, bend the oil pickup, and ruin the motor while the driver may not even suspect any serious damage yet.
Though a good skid plate should protect any oil pan.
Or one could make a bash plate, similar to the JUN pan.
