Malvern vs AISHK vs ICS

My son is 4 years old. Since this is our first child, we don't have much ideas of child education and have cast the net when applying school for my son. Luckily, my son received offer for admission to reception class (equivalent to K2 in HK local system) from various international/private schools starting from next school year. We have already crossed out some of them mainly based on impression we got from talking to the teachers or admission people at the school tour and negative comments we have seen in public online forums. Now we have come to point of making a final choice among the shortlisted schools: Malvern vs AISHK (Aus) vs ICS - we see good comments on these schools so far. We understand that these schools are very different in terms of curriculum (UK vs Aus vs US) and college entrance examinations (IB/HSC/AP) but i don't think it matters much for now as i see these schools did have student placements into good universities in UK, US and Australia - these are the most common places for university study.