It's hard to say which is best. It depends on what you want.
ESF has a play-based approach. The teachers seem very experienced and are all non-locals. The students are very international. Getting into ESF kindy used to give the child priority to get into ESF primary school, but I don't think that's the case anymore.
My son goes to Deborah. I decided against ESF as he was waitlisted with a high chance of getting in, but an afternoon place. Deborah has a more structured curriculum, but lots of fun elements. They have a theme around which lessons are structured. The teachers are younger, so maybe some of them are not as experienced. There are some non-local teachers but both my son's teachers are Chinese (but with fluent English). My sons classmates are a mix of locals and non-local kids. The fees are really reasonable, though they have different uniforms and books etc which makes the cost add up. I'm pretty happy with the school, and it has a good reputation but I have to say my son doesn't like going to school. But that is very probably related to him and not the school. Both my husband and I disliked school too, so maybe it just runs in our genes.
I always mix Greenfield and Greenville up. The one just opposite Hang Hau MTR in Nan Fung Plaza must be popular because once I saw a massive line of people outside queuing for admissions.
A newly opened school in Yau Tong is Mills International. It's got a similar feel to ESF, with experienced non-local teachers. However, I think the curriculum is a bit more structured than ESF. They stressed they would prepapre the kids for primary school admissions. They have an open day on Sunday so you could check it out. The fees are about HK$6000 a month though.
There's also Garden House in Clearwater Bay that follows the Waldorf method.
There's Learning Habitat in Lohas Park which has a bilingual programme.