Though I don't fly either SQ or CX as much as (admittedly very, very inferior) US-based carriers, my default when I fly one of them trans-Pacific (always in J) a few times a year is CX. As others have noted, CX is much easier to deal with on the ground. To pick just one of several experiences, trying to book an SQ/Virgin RTW J class was such a hassle that I simply gave up. Plus as a OW Emerald CX treats me much better (including occasional upgrades to F) than SQ does for my equivalent status with *A.