Thanks.
While Delta points don't expire, it looks like I will get fewer points from them because it's a Delta-ticketed flight and it looks like Delta is giving points based on spend, rather than distance. Also, from what I'm reading here, Delta's removal of award chart means it's too unpredictable when claiming a reward. Is that true for many?
So that would leave it between Alaska and Flying Blue. Any particular reason to pick one vs other? They both look like they will give me the same points for this trip.