Try CX J once and see whether you can put up with the new seat. However they sometimes use the old slanty seat on the AKL leg so you might not get to try it.
The CX J seat you also have to sleep on an angle, and your feet are sticking out in the aisle, so they can often be brushed or fall off the footstool. So you have the same issues as the SQ J seats, with no upsides of wider seat and protected footwell.
I suspect after you try the new CX J seat once, you won't want to continue using it compared to the new SQ J seat.
Im not so sure that the CX J seats require you to sleep on an angle to the extent that the SQ J ones do.
Other points: The food on SQ and possibly cabin service can be better than CX. The cabin ambience created by the layout of SQ's J class may also be better than the 'feedlot cattle' feeling you get in CX's J class.
However, from what I can gather, CX treat their upper tier FF better than SQ do, and as you say, the timetabling and scheduling is better. I have a feeling SQ may also be more expensive as they place a premium upon their A380 and 773 J, F and R seat prices.
CX F may well solve all your problems.