Airbnb makes sense if a group wants to stay together instead of splitting up into 2-3 different hotel rooms. It is also slightly cheaper compared to hotels especially for bigger groups. If you don't need hotel amenities, Airbnb is a good alternative and lots of Airbnb actually have better locations compared to hotels. Some people also book Airbnbs for 2 pax maybe for location and probably washing machine. Price is not that different from hotels for 2pax and I'd definitely choose to stay in a hotel if I'm traveling as a pair.
Not sure what you mean by shops, shops at the airport? By the time you clear customs and get luggage it'll be 7am and most restaurants are open. I take Korean Air 3-4 times a year and they are ok. One thing is they don't turn on the AC and it gets pretty warm for long flights, so I changed back to taking SQ when I'm going back to SG (I'm based in KR).
