Marriott Rewards just announced their latest airline partner Iberia. You can now earn Iberia Avios for your Marriott stays, although this makes very little sense.
Iberia is part of IAG (International Airlines Group), as is British Airways. You have been able to earn BA Avios for your Marriott stays for a long time. You can freely transfer Avios between Avios, BA Avios and Iberia Avios, so there has been a way to earn Iberia Avios for your stays for a long time.
I would neither do a straight conversion of Marriott Rewards points to Iberia Avios nor using the table on the Marriott press release. If you really want to convert your Marriott Rewards points, you should do it via Marriott Travel Packages (you can read more about them here).
Marriott has airline specific promotions at times. I would wait to see if they (Marriott) or Iberia offers a bonus for either converting rewards points to Iberia Avios or for crediting stays directly.
It is always good to have more airline partners, although there has been a way to get your Avios to Iberia Avios via BA. Let’s hope that they would offer some juicy promotion to celebrate this new partnership.