Do you care where you collect your miles ? SQ and UA are sorta kinda star alliance and SQ is a bit strange so check if you can accrue miles on your potential SQ frequent flyer account

I hear Korean air food is better. United Coach food is nothing to write home about I hear

I'd pick Korean.

United in-flight service varies from indifferent to aggressive.

United food in economy is sub-par. Though after a number of UA flights some years ago I worked out that if you pre-order a Hindu Veg special meal you get a pretty decent plate of curry and of course get your food before everyone else.

Korean will fly you in more comfort: their A330 and A380 aircraft are marginally more comfortable in economy class than the narrower, densely configured 787. For the return flight on the 777, Korean is one of the handful of airlines that has retained the more civilised 9 across seating on that aircraft rather than 10 across. What that means is the same number of seats in each row on a Korean 777 as UA cram into the 787 which is 550cm in diameter vs 590cm for the 777.

The stop in Seoul might be good to let your kids run around and let off some steam mid-trip. The transit process is very easy and Korean Airlines just moved into the brand new terminal 2 at Seoul airport.

The food on Korean is great - if you like Korean food. Western options are edible but unremarkable.

One area that Korean falls short of UA is the choice of English language in flight entertainment. There's a bit there, but not a lot. And another shortcoming is the weird service timings on trans-Pacific flights where they wake the whole cabin up for a meal service about 4 hours before landing, clear it away and switch the lights off again. Oh and they insist on blinds being closed on day flights; too bad if you like to look at the planet from above.

Despite those shortcomings on Korean, I'd still pick them over United.

"..One area that Korean falls short of UA is the choice of English language in flight entertainment..." - but it's fine for those of us that are Korean TV drama fanatics :P.

United is not the worst airline I have used, but it falls below nearly every Asian airline I have used.

United flies SFO-SIN non stop. UA1 departs SFO at 10.40pm, arriving SIN 8.00am +2. That would be more convenient time wise. You can also fly via Tokyo Narita (NRT) with a connection to ANA. United and ANA are joint venture partners. That said, for economy I would much prefer the 787-9 over the 777-300ER (10 across).

I'd take an Asian flag carrier/airline anytime before I'd take a US one. It's all about Customer Service which doesn't exist, sadly, with US Airlines. Food is usually better too.

No it's all about price, routing, flight times, inclusions. Service is rather comparable across most airlines. Obviously some are better than others, Korean will be a step up, but I won't be deciding a flight halfway around the world based on whether or not a FA smiles twice instead of once and my 4 dollar meal was marginally better. The choice is yours.

How strange! To think customer service is down to whether staff smile or not. I'd pick KE assuming cost similar, even if there was a stopover. And I do. But a lot of things make customer service, in my opinion. Primary is whether people notice things or deliberately don't. In a recent flight on KE the crew told everyone to sit upright while meal service and eating went on, which helped us hugely. On the same flight an FA said " you look tired, let me make you a cup of tea," to my wife. I've had good experiences on UA but the KE is way better on average.

Thanks R_Squared_12, belomiser, ByronMagik, WarrenL, UDBusinessTraveller, WEQueen, wanderer05, ethenman for the valuable inputs and advices. I will follow most of the advice: KOREAN air. Many thanks guys..