To answer your question about AM F vs. DL F, food and service are about the same. If AM happens to run the 787 on this route and you haven't taken it and are interested, it could be worth it. The 787 is a novelty that wears off quickly, but AM does have flat beds in F on the 787.
BTW I have seen similar mileage redemptions to Mexican destinations as you; 60,000 for AM F and nearly the same, if not higher, for DL coach.