I would definitely say Emirates. I am able to buy really good Business/First (usually Business as low as full-fare Y or just 10% above) fares on Emirates through "ethnic" travel agents to DXB, DEL, BOM from London. And almost always I have had a choice of AA, UA and Virgin across the Atlantic. I usually pick AA to LHR since I am Executive Platinum with them. I get my EK flights posted to UA and have never had a problem with the miles not showing up.