The funny thing is that most people choose Elixir over Erlang because of the syntax - personally I can't stand Ruby but love the Erlang syntax. When I see Erlang code, everything just clicks - almost like I'm reading prose.
So, if you want to harvest the power of Erlang, I'd suggest you start with the real thing first. The only drawback is that once you get used to functional programming, guards, pattern matching, OTP, cheap processes, links and all the other goodness, there's no way back.
If you still feel Erlang is weird after spending a couple of days working with it, feel free to jump on the Elixir bandwagon. :)
I would say it goes much deeper than syntax and both Elixir/Erlang can co-exist happily just like Scala/Java. After jumping into Elixir, you'll eventually have to become familiar Erlang/OTP conventions, but starting with Erlang is not a requirement. You're right that guards/pattern matching/OTP leave you with language envy once you go back to your previous language of choice. Elixir does remove some pain points of Erlang, particularly around metaprogramming, polymorphism, and string handling. I will say after getting into the ecosystem, I can't believe the Erlang folks have been quietly "building the future" all these years while the rest of us largely ignored their innovations.
Personally I don't find Ruby and Elixir to be very similar. Maybe some of the terms are the same, but in general they feel very different. Elixir has a much more consistent syntax than Erlang (imo), it's macros are more powerful, it has a great build system right out of the box (inspired by leiningen for Clojure), and it can make use of any Erlang library with no additional effort. I'm also a huge fan of Elixir's pipes feature, which I think makes a lot of code much cleaner and easier to read. I love Erlang, but I wouldn't call the use of Elixir over Erlang a bandwagon - there are good reasons why one would favor Elixir as a starting point. There are probably reasons why one would choose Erlang instead too, but I feel like if you are at a point where you can choose one or the other, Elixir makes the most sense.
Erlang syntax is a) Prolog inspired and b) more than 20 (closer to 30) years old. While it generally gets the job done without much hassle, it's very possible to improve on it. The macro system you mention is the reason I'm going to give Elixir a whirl, despite being happy with Erlang otherwise.
Anyway, the situation of Elixir and Erlang looks more like JavaScript and CoffeeScript to me than like Java and Scala. Of course, Elixir is similar to Scala in terms of implementation - they both compile to bytecode instead of transpiling like CS. But the features Elixir brings to the BEAM are less groundbreaking and more practical, just like in CoffeeScript and unlike Scala, which transforms JVM so much that it's almost invisible.
There's a difference, too - JS is being reworked and Harmony will bring many improvements which Coffee has today, but I'm not aware of "next generation Erlang" being actively worked on (Joe Armstrong does erl2, but I don't know how active it is). So while there are people who don't use Coffee because "it will be in the standard in a year anyway" this argument does not hold true for Erlang and Elixir.
Just some random thoughts, I like them both and am actively learning Elixir while maintaining a project in Erlang (and I also like Scala!) and I hope they can both thrive. It's a symbiosis, really - Elixir brings a new wave of developers to Erlang, and Erlang gives a solid foundation to Elixir.
Respectfully, I'm not sure I buy this comparison. Yeah, CoffeeScript adds some cleaner syntax and OO niceties onto JS, it's still basically just a higher level abstraction that get boiled down to JS. Elixir is a multi-paradigm language that that gets turned into the same type of byte code that Erlang does and is interoperable with Erlang. Its more like jRuby and Java both living on the JVM and being able to call Java code in jRuby, or maybe its a bit like ClojureScript and Clojure?
So, if you want to harvest the power of Erlang, I'd suggest you start with the real thing first. The only drawback is that once you get used to functional programming, guards, pattern matching, OTP, cheap processes, links and all the other goodness, there's no way back.
If you still feel Erlang is weird after spending a couple of days working with it, feel free to jump on the Elixir bandwagon. :)