Having flown both SQ and CX recently (SQ in all cabins both regional and long-haul, except transpac Y; CX in regional Y and regional J), I agree with most of what Carfield posted. I will add something, though. Flying regional Y on CX, I felt like we were getting a bit of the old cattle class treatment, whereas SQ delivers high-quality service and quite good food even on regional Y. That's where, I found, CX and SQ diverge the most in flight, while the Wing far surpasses SKL on the ground.

Now for the part where I disagree with Carfield. Singapore Boys are better looking and friendlier, overall, than Cathay Boys. Personal preference, but it's based on a broad sampling and extensive experience.