Originally Posted by MarkXS

I'd recommend either Skyteam or *A over oneworld based on these factors: multiple US-based carrier choices rather than just one, and multiple European hubs that have major connections. Also ST and *A don't have the restricton against earning transatlantic in a USA-based program from an European-based carrier that makes BA US-UK worthless to AA members (and conversely, AA US-UK worthless to BA members).

If you think that you could hit 50,000 BIS (butt-in-seat) miles in one alliance, I'd then narrow it down to *A. 50,000 in United's program gets you mid-level elite on United like it 50k does on anybody else. But mid-level elite on United (or on most *A carrier programs) gets you top-level Alliance-elite, Star Alliance Gold. That gets you lounge access on international itineraries. 50K-level elite in the US-based Skyteam programs (CO, DL, or NW) only gets you lowest-level alliance-level Skyteam Elite instead of Skyteam Elite Plus. So no lounge access.