In terms of hard product:

NH, BR, and CX use the same W seat; it's a standard-fare recliner, generally 38" of pitch and ~19" wide. CX's W cabin on their A359 will feel more cramped since it's still 2-4-2 despite a narrower cabin versus a 77W.

JL and CI use the same W seat; it's a slide-forward semi-shell. JL has 42" of pitch and ~19"-wide seat while CI has 39" of pitch and 20"-wide seats (2-3-2 in their A350s). As long as you're okay with the slide-forward style of recline, either of these two will be the roomier option versus the other carriers. CI's W seat also reclines a surprising amount (their W seats on their 77Ws feel like they barely recline).

In terms of soft product, it's honestly roughly a wash since it's all going to be fairly similar. But I wouldn't expect fancy snackbar access (although you might be able to sneak into CI's since the W lavatory is right next to it, which I still find really awkward).

It's worth noting that until CI introduced their W product, the last time I flew in any sort of "premium economy" was Evergreen Deluxe in the nose of a 744 Combi.