I would probably go for the C & K.
I'm not that keen on Montessori, really, despite having gone to a Montessori kindy myself. I'm all about freedom within play, and "true" Montessori doesn't really encourage that - each set activity has a set way to carry it out, and the child will be corrected by the teacher if they're not doing something "properly" I think that every child has enough chances in their life to be told they're doing something wrong, so why start early?
If they don't operate this way and it's not a "true" Montessori kinder, then they're using the name as a gimmick to attract a certain kind of parent. Which I also don't agree with. But some people, like my mum, love the Montessori method.

That's my $0.02