Through Nov 15, 2018 you’ll get 1,400 Avios for every 1,000 Amex points you transfer to British Airways or Iberia.
The best uses for BA Avios are shorthaul Oneworld flights (on AA domestically or in Europe on BA or Australia on Qantas).
The best use for Iberia Avios are from the eastern part of the US to Madrid in Business Class for 34,000 each way.
The downside is that I find Amex points much harder to earn than Chase points, which transfer 1:1 to Avios. Still, 40% is pretty sweet.