Living in the UK, and prefering direct flights, i've always used Thai or EVA, well, nearly always EVA.
I think the overall experience is better with EVA, and they are nearly always cheaper. We're booked for mid January, me the wife and our infant daughter, in total cost £940.
I have flown Thai before, but that was before they changed/upgraded the aircraft? I found the then aircraft and fixtures looked a bit dated compared to EVA, the general attitude etc wasn't as good as EVA.
Has the Thai upgrade made them better?
Thing is, Thai fly twice a day from London, compared to EVA's once, and Thai are consistently more expensive, so more people must prefer to use them than EVA.
I know Thai people sometimes prefer to fly them, and London has a big community, but that many? My wife is Thai and has flown both, she actually prefers EVA. But again, that was before the aircraft change/upgrade.