for SQ... i don't think you will get the new sky bed for sure..
only SQ 1 receives skybed for ex-Hong Kong... at least when I travelled on SQ 857 and SQ 861... I got the three class B777-200.. with normal business class seat..
for CX.. i tried both the NRBC and RBC (regional Business class)... the NRBC is no match compare to SQ's skybed.. however, both NRBC and RBC are almost idential to SQ's regional business class..
Since HKG-SIN is approximately 3 hours.. SQ or CX won't caused any problem..
Personally I will choose CX because it is my preferred airlines.. and miles