The paper from HAL is irrelevant. It deals with denied boarding compensation and you were not denied boarding. You say that you were delayed. That is a different part of EC 261/2004. Unless the delay was due to an "extraordinary circumstance" ("under control of AC is irrelevant"), you are due EUR 600 in cash or cash-equivalent.

Why was your flight delayed? That is a critical question.

If AC wishes, it may also offer a voucher, typically for more than the cash amount. If offered, you may choose to accept that. But, do understand that it is entirely your choice. I would not be so quick to reject a voucher. It all depends on your needs and your flying patterns. You need to check its terms carefully. If you are a regular flier, you could use a voucher to purchase tickets and thus do 50% better. But, if you are an infrequent flier and don't use the voucher, you lose all the value and are better off with the cash. Don't jump one way or the other without some serious thought.