GCP Cloud Storage: What is the difference between bucket.upload and file.save methods?

Is there a better option for uploading a file?

In my case I need to upload a lot of small files (pdf or text) and I have to decide the best option, but anyway are there differences between these two methods?

Here two examples taken directly from the documentation

Save method: (Docs)

const {Storage} = require('@google-cloud/storage');
const storage = new Storage();
const myBucket = storage.bucket('my-bucket');

const file = myBucket.file('my-file');
const contents = 'This is the contents of the file.';

file.save(contents, function(err) {
  if (!err) {
    // File written successfully.
  }
});

//-
// If the callback is omitted, we'll return a Promise.
//-
file.save(contents).then(function() {});

Upload method: (Docs)

const {Storage} = require('@google-cloud/storage');
const storage = new Storage();
const bucket = storage.bucket('albums');

//-
// Upload a file from a local path.
//-
bucket.upload('/local/path/image.png', function(err, file, apiResponse) {
  // Your bucket now contains:
  // - "image.png" (with the contents of `/local/path/image.png')

  // `file` is an instance of a File object that refers to your new file.
});