KWA, due to very different business principles.
KWA does a good bit of internal innovation and few external variations. Their outlook is centered on ballistic performance. KWA wants to get your money by selling you impressive figures and numbers. I've been fairly impressed with the most recent KWA AR AEG I've seen (I'd hold out and see if KWA comes out with even better models).
CA does a lot of external variations, but has been relatively inactive on the internal innovations front. CA's also been somewhat distracted with its downward race against the Chinese clones in the last few years. CA wants your money by selling you what you can increasingly better afford. I've never been that impressed with the CA AR AEGs I've seen.
"The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."