Only heard good things about SWCK, but i never delved into the details. The continue of SWCK is ICA, which also receive lots of positive comments.
CDNIS & Victoria are both IB school, but Victoria is more bilingual (or trilingual at an earlier age). It really depends on how much mandarin you want in a school in the long run.
Note that CDNIS only interview Cdn passport holder starting this year (2014 entry) since they have too many applicants.