Although I am a Loyal CX MPO, however based on your options I think SQ is better. To be honest who cares about service in Y Class. As Long as you don't get treated like on AA or any other US airlines you should be OK. The exec Y Class on SQ seems to be a more comfortable seat than CX (given the pitch and also the width - 2-3-2 VS 2-4-2.

Are there any plans foy Premium Economy in CX?