Which mode for Ethereum?

[while1]

Hello!

I see that there are two separate modes for Ethereum:

15600 = Ethereum Wallet, PBKDF2-HMAC-SHA256
15700 = Ethereum Wallet, PBKDF2-SCRYPT

When looking in my keystore file I see the cypher is aes-128-ctr and "scrypt" is referenced as the kdf:

{
    "crypto" : {
        "cipher" : "aes-128-ctr",
        "cipherparams" : {
            "iv" : "..."
        },
        "ciphertext" : "...",
        "kdf" : "scrypt",
        "kdfparams" : {
            "dklen" : 32,
            "n" : 262144,
            "r" : 1,
            "p" : 8,
            "salt" : "..."
        },
        "mac": "...",
        "id": "...",
        "version": 3
    }
}


Which mode should I be using?