We were in the same boat. But we chose ESF (Tsing Yi) as we couldn't make up our minds at that time and it offered 3 different types of school for our catchment area. Yew Chung was one of the schools we considered but are glad to have not gone down that route. ESF(TY) has provided an education no better than what he would have gotten at home (Australia) for his age group and cannot be compared to other schools that cater for the local market.
Some advantages of ESF:
(1) Great interview preparation/opportunities: All 3 schools we have applied to are oversubscribed, ESF (TY) released the group list for all kids and we got together very early for group playdates. And, if you fail an interview (with the exception of Discovery College), you can lots of chances to pass and a lot of effort will be made for your child to ensure placement.
(2) Teachers and T.A.s are wonderful and caring. They do take time to get to know your child (despite the large classroom size) and are often happy (or at least appear to be happy) to chat. Emails are often replied within the day. We have been extremely lucky to have had 2 years of just absolutely wonderful teachers and T.As. Even if you met them out of school, they're just as friendly!
(3) Less focus on showy things. There's actually a lot of curriculum time spent on learning (through play). No showponnying business that a lot of schools engage in using curriculum time.
Disadvantages of ESF(TY) - which did not bother us i.e. not disadvantages to us:
(1) If you're a native speaker, be prepared for your child to come home speaking like a non-native speaker - sentence structure wise e.g. ours started dropping his articles.
(2) Do not expect your child to know how to read or write in Year 1/2 like their local counterparts. Mine is in Year 2 right now and he's only expected to write his name. It is not a school that focuses on academics.
(3) There is no Putonghua emphasis at the school. Once a week is all your child will get. (If this is important to you)
We have so far been happy with the school. Learning through play has had a wonderful effect on our child. Now that interviews are over, we are very glad that we've sent him to this school as without it we wouldn't have had a leg up (so to speak) to get into one of their up and coming schools which has a heavy emphasis on Putonghua. So we would be choosing the same route for our 2nd child too.