I had the chance to compare AY C with that of AF and KL - AY was a tie with AF and considerably ahead of KL. (It's been a long time I had no direct aisle access in longhaul C - KL's 2-2-2 made me climb over my neighbour's legs)

The hard product on AF was slightly better (very similar seat to AY', but better legroom/footwell), the catering was maybe a notch below AY on a good day. This being AF, the wine selection was good, but it's good on AY, too. KL's offering was the least good of the three (I cannot say worst, as it was good, but least good)

The service was again a tie between AF and AY (on a good day with Finnish crew), KL was a tie with AY (on not a good day with Finnish crew)

Interesting excursion to the uncharted waters of ST and saving a LOT of money in the process (WAW-Japan was 1500€ in front of the bus via CDG outbound and AMS on the way back - thanks the relevant FT thread for the info! ^ Skipped the last leg out of AMS, came home on HE - probably first and last flight with them. Still, the AMS-WAW boarding pass gave access to pro security and Crown lounge)