I flew BA in first two days ago from London to Bangkok; SQ last month in F from LAX to Singapore and return; and UA frequently in F from LAX to Bangkok and Singapore. I'll be flying CX in F from Hong Kong to London in a few weeks so will then be able to compare the four with recent experience on all of them.

Right now, SQ wins hands down. Best seats, best service, and best food. Yes, they had duvets on the long hauls (but no cavier).

BA comes in second. The suites are sized like United's, but are more elegant. The service was professional and adequate. Food was good--not great, but I have no real complaints. The flight attendant told me the seats were recently redone with additional padding. BA was fine, but the suites are noticeably smaller than SQ's.

United is utilitarian. The 747 cabin is cramped with 14 suites (configured like BA's). They are a full inch narrower in the seat than those on the 777 (which is a spacious cabin). The suites are starting to show their wear and would never be described as elegant. The food is ok and the service perfunctary. The best feature is the large storage bin for all your goodies during the flight. SQ and BA lack those.

I rate these three in that order. I expect that CX will fit in between SQ and BA, but I'll give them a fair chance. It'll be an A340, so I'll probably complain about traffic through the cabin. We'll see.