Sorry you're going through this - and congrats on the milestones!!

If I were you, I would stick with DL on the return. I just flew VS to LHR recently; and DL on the return and much prefer DL. As others have noted, you will get Upper Class Lounge at LHR. The only real thing you will miss are the "sleep suits" (i.e. Pajamas which VS gives but Delta doesn't). I have flown most planes in both fleets and unless you get the very old DL 767-300 or VS A350, you are better off flying DL. I think the odds of either of these aircraft are low from US to/from LHR.

Here are onboard Virgin pics to LHR on the A330.

Oh, and on Virgin you would get a "rich people" can of water which no one knows how to open




VS breakfast. I don't eat at 11 p.m. and so skipped dinner...

You get a mattress pad to put over the seat. But also, the seat can't really recline the way DL can. Instead you have to stand up and it basically flips.