We like the YMCA Kindy alot too, but we have friends with kids at ESF Tsing Yi and they seem happy with it (but obviously we don't have direct experience with it). Both kindys are play-based but YMCA seems a bit more structured. YMCA has a full day program option in K2 but I don't think ESF does. Both teach a little bit of Mandarin as a second language only so if you mean Chinese language development, I don't think thats a strong suit in either school. If you want your second child to go to ESF Primary and you don't have sibling priority through your elder son, then you can get priority through being at ESF kindy. If this is not a factor, then YMCA is really good and lots of kids there, even this year, have been accepted into ESF Primary.