I think it all depends on what do you mean by “good”, “better” or “best” terms. What is your perspective? If you look from business perspective, and need MVP as fast as possible, then the tool (framework) that let you build applications fastest way, and let many people just jump in and start coding, is really the best tool.
But then again… Rails may be better, or XXX framework, because there are not really many people using Elixir and Phoenix compared to Rails or many other frameworks.
If by “best” you look from perspective of code maintenance, purity of implementation, ease of testing and code (implementation) readability, and all of those things that business side probably does not care at all… then, well I think there are better languages/frameworks than Elixir/Phoenix.
But if you want to combine the speed of code delivery with easy of maintenance and readability, then you need to sacrifice some of advantages from either side. And because of this trade-offs, from one side Elixir/Phoenix is really great combo (and is actually my tool of choice for web related stuff i do at work), on the other hand we can’t really say about any framework being “best”, there are many “good” solutions and if one is “better” than the other depends heavily on context.
When I was reading first about Raxx I though, great… it’s rack-alike, so it probably sucks hard, like IMHO rack does (but I really know only weak sides of rack, and simply discredit any good there may be 
). But after watching it for a while, i really, really dig the idea. I love how it’s simple and clean to stream data in Raxx, it’s the “best” 
way to handle it I’ve seen so far.
So TL;DR “BEST” Really depends on context.
