What is the difference between using string and buffer in Node.js encryption

I saw both of the codes below on some websites. One used Buffer to wrap crypto.randomBytes() object for cipher key and used it to concatenate the final result of the encryption, another one used plain crypto.randomBytes() object for cipher key and simply concatenate the final result using 'plus equal' operator.

const cipher = crypto.createCipheriv(
  "aes-256-gcm",
  Buffer.from(crypto.randomBytes(32)),
  crypto.randomBytes(16)
);
let encrypted = cipher.update("this is data");

encrypted = Buffer.concat([encrypted, cipher.final()]);
// edited: I forgot below line
encrypted = encrypted.toString("hex");

and...

const cipher = crypto.createCipheriv(
  "aes-256-gcm",
  crypto.randomBytes(32),
  crypto.randomBytes(16)
);
let encrypted = cipher.update("this is data");

encrypted += cipher.final();

Both implementations work. But I can't find any explanation on why do they use Buffer and don't know what the difference between the two examples is.

UPDATE

I've tried using the same key and iv with both implementations (as Maarten Bodewes suggested, they produce the same result:

const crypto = require('crypto');

const data = 'hello world'
const algorithm = 'aes-256-gcm'
const key = crypto.randomBytes(32);
const iv = crypto.randomBytes(16);

function encrypt1(data) {
    const cipher = crypto.createCipheriv(algorithm, key, iv);
    let encrypted = cipher.update(data, 'utf8', 'hex');

    encrypted += cipher.final('hex');

    return encrypted;
}

function encrypt2(data) {
    const cipher = crypto.createCipheriv(algorithm, Buffer.from(key), iv);
    let encrypted = cipher.update(data);

    encrypted = Buffer.concat([encrypted, cipher.final()]);

    return encrypted.toString('hex');
}

const result1 = encrypt1(data);
const result2 = encrypt2(data);

console.log('result1: ', result1); // -> result1:  501db5c82e79e3185c1601
console.log('result2: ', result2); // -> result2:  501db5c82e79e3185c1601

So, why do one have to use Buffer which looks more complicated to produce the same result?