Kind of depends what you mean by "best". What's important to you?

Middlebury has a lot of things going for it and would be on my short list. It's going to be more rural than Burlington or Essex.

I lived in Essex for 8 years and liked it very much. The schools are quite good and it's conveniently situated to many things (mountains, airport, Burlington, lake).

The Burlington "metro area" has a lot of great places to live - Shelburne, Charlotte, South Burlington, Williston, Colchester all have good schools and communities.

I wouldn't necessarily exclude the other towns, I just don't have as much personal experience with them other than visiting occasionally.