The AA FF program is similar to MP, in the sense that you get systemwide upgrades (eight of them, called eVIP's), and you also get unlimited domestic upgrades within region one. Unfortunately, their best partners, especially BA, don't allow you to redeem miles on them from the US to Europe. I would say that UA really is your best option, even if it's not great.

Most importantly, welcome to Flyertalk, sergio10!^