Welcome to FT! I'll add my voice to the chorus...ditch Delta and go for EXP. I can speak from the current experience of having been both DL PM and AA EXP for the last 3 months. For purely domestic travel, DL PM has a few advantages (unlimited free upgrades on the higher coach fares confirmed at booking, free club access). But if your travel is mostly international (as it seems yours is), AA and EXP have the edge...VIPOWs which can be used on any fare, the possibility of intl F/C travel, great lounge access. Not to mention MRTC!

Just burned my first VIPOWs to upgrade $500 intl tickets to J - it's been 10 years since I had an upgradeable DL intl fare that low. I am not going back!