I always liked die cast - I have Lionel 700 series and the MTH hudson in die cast.
The early 700T had a horrible record of disintegrating - fortunately, repros abound.
I now prefer lost wax or lost plastic brass, bronze, or nickel silver. It is more expensive, but with newer 3 D printers costs may be coming down.
I am lusting after an MTH Bi-polar at the moment. Any reports of faulty castings in them?