Ok - I need just 3k miles for the next status level on Detla and just 4k miles for the next status level on United. I have one trip coming up on the 31st of December. I can qualify for the next level with either airline (Delta or United) but not both. Questions is - If I can only get enough for miles for the next level on just one airline - which one am I better off doing? Would I rather be Premier with Delta or United? The hub city makes no difference as they both fly where I need. So all things being equal, which program should I do?

Thanks!