Originally Posted by nanyang

Have done the SIN route on both a few times.

AY:
- As noted above, 1+2+1 seating layout in J, so more privacy
- Much more relaxed experience with the connection at HEL (I'm sure the new Istanbul airport will be an improvement vs. the current chaos)
- European J class has blocked middle seat only, but I find the experience generally acceptable for a 3h flight (food and service fine based on my experience)
- Lounge is ok but food options are very limited - lounge def not crowded around 11pm (HEL-SIN departure); if you have status in oneworld, then you get access to the nicer part of the lounge
- IFE content is very weak
- meal ex-HEL on the HEL-SIN sector not that substantial (I usually bring protein bars with me for AY flights) // other meals have been fine from what I recall
- Transfer security at HEL coming back from SIN will be much less hassle than IST
- Gates will be next to each other (vs. a fair bit of walking at IST)

TK:
- I assume proper 2+2 seating on the European sector
- Food traditionally good, but I recall they changed their catering company (haven't flown TK for 12 mo or so...)
- I find connecting at IST (current airport) a bit stressful; connecting security is chaotic, and be prepared to walk a fair bit (also the IST-SIN flight had a bus transfer last time I took the flight)
- Many people seem to talk about the IST lounge; technically it's nice, but can be very crowded and not a relaxed experience at all
- Long-haul J seat is fairly comfortable, but no privacy (and no aisle access from window seat)
- If you miss your connection, dealing with TK likely to be more hassle vs. AY (having said that, haven't had to deal with TK customer service at IST for years)

--> Both options are fine. Would not hesitate to book this trip with either airline.