The best latex editor I used so far is TexPad ( https://www.texpadapp.com ), but it's only available on OSX and iOS...
Could you elaborate on that? What makes it the best for you? More to the point, in what ways is it better than AucTEX?
* It's a standalone and native OS X application
* It has code completion
* File and document navigation is easy thanks to tree view
* It works out of the box, no dependencies other than TeX required