What are the advantages/disatvantages to specify a struct param in a function as calldata vs. memory?

Question

If I am not modifying the input parameter in the function body are there any reasons a reference type parameter should be labeled as stored in memory?

More generally what are the reasons to go for function foo or bar below. ( the same question goes for other reference types like strings)

function foo(StructA calldata asCallData) external {
    ...
}

function bar(StructA memory asMemory) external {
    ...
}

Answer 1

Using calldata is cheaper, consumes less gas. However, the disadvantage is that you can't modify the received data, it's read only.

Example based on your code:

//SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract BasicContract {
    struct StructA {
        uint varaiable;
    }

    function foo(StructA calldata asCallData) external {
        asCallData.varaiable++; //This will not work
    }
    
    function bar(StructA memory asMemory) external {
        asMemory.varaiable++; //This will work
    }

}

Therefore, if you are just receiving values/data to store it into the contract, using calldata is the preferred method:

Case and point:

//SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

contract BasicContract {

    struct StructA {
       unit varaiable;
    }

    StructA data;

    // Cost: 23817 gas
    function foo(StructA calldata asCallData) external {
        data.varaiable = asCallData.varaiable;
    }

    // Cost: 24182
    function bar(StructA memory asMemory) external {
        data.varaiable = asMemory.varaiable;
    }

}