CakePHP 3.6：速度优化（包含或loadModel）

Question

Is there any difference when using contain or loadModel in terms of speed and/or resources?

For example:

$transaction = $this->Transactions->get($id, [
            'contain' => ['Customers']
        ]);

$customer_name = $transaction->customer->name

VS

$this->loadModel('Customers');
$transaction = $this->Transactions->get($id);
$customer_name = ($this->Customers->get($transaction->customer_id))->name;