One advantage of white metal over styrene plastic is strength.
Metal parts will not warp under the weight of a built model regardless of the size of the aircraft, no matter how many years it stands on display.
Another advantage of white metal is the way it holds up under "working" conditions (drilling, scoring, sanding, etc.), as it is much more dense than styrene plastic and has a much higher melting point.
Being quite malleable, it can be bent without the fear of breaking & a useful characteristic when it comes to final alignment "tweaking".
Parts are cast in a Lead Free Pewter by Scale Aircraft Conversions