Just returned from PEK last night. I flew DL there on the A350 and UA home on a Polaris-remodeled 777. The seat is a LITTLE nicer on DL, but the entire idea of it being a "suite" is more of a gimmick than anything. Food....DL was better. Lounge experience, no doubt whatsoever goes to UA. The Polaris Lounge blows the SkyClub out of the water. It's like comparing Sax to Walmart. I'm Delta's biggest fan, but the comment above saying there isn't much difference between the clubs couldn't be more-wrong.

In your case, I'd personally take the UA nonstop..... especially if it is the new Polaris cabin