Have done SEA-LHR many times in BA Club World. Decided to give new DL35/36 Business Elite service a try this time. Found it quite superior to BA in most respects. A few key differentiators:

Timing: convenient both ways. Certainly better than the BA early afternoon departure from SEA which is a nightmare for jetlag.

Seating: DL is all forward facing, with every seat having aisle access. This is a significant advantage. 1-2-1 configuration as compared to BA’s 2-4-2. None of that weird BA thing of staring into a strangers’ face until you put the screen up. Some flyers have complained about the lack of foot room on the DL lie-flat seat when lying down, but I didn’t notice this and got good quality sleep. Very nice comforter and a deep soft pillow – again superior to BA. For single travelers the aisle and window option with the tray on the aisle side (odd number rows) gives great privacy.

Service: BA is always polished, but DL has a more informal, personal and welcoming style, and they address you regularly by name. Met the relief pilot mid-flight at the galley, who was happy to chat about the plane and the route, and thanked me for flying Delta. Typical company touch.

IFE: I am not a heavy user. But excellent resolution screens and good selection of movies and music.

Food: much better on DL. More courses, more substantial, higher quality, nicely presented. Home-baked style breads, spectacular dessert trolley like in the old days! Good wine selection. The Jacquard Mosaique champagne is a particularly excellent choice. Also a nice Selbach Riesling which dealt well with the altitude. Attendant was unhappy about the temperature and took bottle away for re-chilling before pour. Nice touch.

Equipment: DL’s 763 has a slightly noisier cabin than BA’s 772 and 773, but with Bose noise canceling headphones it doesn’t make much difference.

Lounge: DL lounge at SEA is more or less same quality as BA’s, but DL gives you access to the Virgin Atlantic lounge at LHR T3 which is fantastic. You could spend all day in it and not get bored, and services like shoe shine, manicure, massage, etc are all included.

Overall: Despite long standing BA loyalty, I have to say that DL wins for me hands down on this routing. The strong service and hospitality ethic of the company is noticeable. They are trying to impress on international routes out of SEA, and succeeding. Recommended, and will use in future.