I'm not saying that either book is better. In my opinion Eloquent is for more advanced folks, while Speaking might be geared towards beginning programmers.
I'm working through Eloquent JavaScript (v1) right now and I'm on the chapter dealing with functional programming. Even with the programming classes I've taken in college, I'm finding this chapter to be much more difficult than any of the ones before it. Maybe it's uncommon, but I was never shown this type of programming ever before. Even though I'm progressing through it at a painstakingly slow pace, it's starting to make sense. But for someone who looked at EJS as their first programming book? I can understand why they may quit altogether.
If you are interested in learning more, the video below walks through examples.
The book explains the complete language. I consider functional programming more of a (fascinating and important!) meta-topic; worthy even of dedicated books [2] and beyond the scope of Speaking JS.
[1] http://speakingjs.com/es5/ch18.html#_array_indices_in_detail
[2] “Functional JavaScript” by Michael Fogus. http://shop.oreilly.com/product/0636920028857.do