Airlines can have a few different award allocations. There are seats offered to their own elites, seats offered for redemption with their own points and then seats published to partners. Those can all be the same or they can differ, depending on the company's policies/decisions.
If you are booking on partners anyways then AC is probably the best bet to park the points. If you would potentially be flying on AC then it is a bad choice because of the cash fees (e.g. YQ) that they tag on to their awards.