What is the major difference between 2.x and 1.x?

Basically I'd like to chose the latest version, but the ES-Hadoop seems only supports 1.x now. So I want to know what is the major difference/enhancement in 2.x?

There's too many to list, I'd suggest you read the blog post to start - https://www.elastic.co/blog/elasticsearch-2-0-0-released

Thanks, warkolm.