IIRC All steel ones (quite rare) are generally considered to take more abuse then the cast iron ones, being a bit more flexible, but the cast iron ones should be stronger.
The obvious answer of course is you need all of them, and probably another few as well.
None are particularly suited for beating. All the force will be transmitted into the screw mechanism via the angled moving jaw, supported by the slideways.
A post leg vice is a very well thought out design with some interesting subtleties to the features which make it work.
Obviously one jaw is connected directly to the floor but the moving jaw is bolted directly to it and not floating so it too is “connected” to the floor. The screw is effectively decoupled from any striking forces because it is not directly connected anywhere to the jaws but floats inside locked up with whatever friction holds the jaws shut. They also have a fast acting, coarse thread for getting stuff in and out quickly.
Also the vice body itself is not even directly connected to the bench. A collar holds a separate base with wedges and only the base is bolted to the worktop. The mass of the body (which is substantial) can absorb the shock without transmitting it to the bench. My admittedly quite large version literally weighs more than my anvil!
Much better off beating on a vice designed for it.