It Depend on how will you to use it.
Armored heating elements generally have poor heat dissipation by themselves, and need to be heated to take away the heat in time, otherwise they are easily damaged by overheating.
The cast aluminum heating element has a large heat dissipation area, which can transfer heat to the heated object through air, and can be burned in a short time.
Comparing the heating characteristics of electric kettles (armored heating elements) and rice cookers (cast aluminum heating elements), you can see their scope of application.