Keep in mind that though a few years back it was common to hear things like "any Asian or European airline is going to offer a better experience than a US airline," that is no longer necessarily true, especially if the US airline is Delta and the Asian airline is a SkyTeam partner.

In particular, Delta's Chinese partners are not terrible, but at the same price I'd definitely fly Delta over any of them. Korean vs Delta is more of a toss-up, potentially leaning slightly toward Korean.