Both CDNIS and CIS has adopted the IB program, depends which university you want to send your kids into. Obviously, IB program favor US/North American Uni. GCSE/British Curriculum favor UK university. There are defintely a lot more choices and popular Uni in the US than UK. That explains why IB program is the most popular and international reckon system thats what ESF is also considering to switch to IB pending the government approval.
CDNIS has 30% Mandarin and One hour sessions every day. The rest of the subjects are taught in ENGLISH. CDNIS offers more well round program and in case an expat move to other country, you can easily switch to ANY schools in US/North American/Canada.
CIS is a great school and fully bilingual, high level of Mandarin. However, I found this school very local, very chinese oriented. 95% of the students are Chinese euthinc or Asian nationality. You can see from the graduate classes. I dont think you can find any schools in ANY other country like UK/US/Canada for the same curriculm/bilingual -mandarin and english program schools. To be honest, I dont want my son to turn into a MAINLAND chinese neither. Its the language we want our kids to learn, not the habbit/culture we want to adopt. In case if you leave HK, where can you find the same bilingual program not even in Singapore. No problem in Shanghai and Beijing but not the rest of the world lol.
Forget about AIS, its not IB program.