When the mechanical properties are compared, Alloy 400 is  more ductile and therefore easier to work and shape.
Alloy 400 also has greater hardness and is more suitable for higher temperature use where greater strength is needed than C276. The nickel content of Alloy 400 also improves the weldability when compared to C276. The corrosion performances of the two alloys must be balanced.
Alloy 400 is more suitable than C276 in marine environments whilst C276 is the better performer in acidic or alkaline environments.