I actually like Erlang, but I personally feel it has a lot of rough edges. I'd probably spend a lot of time polishing them to the point where I'd just reinvent Elixir, so I prefer Elixir for that reason alone.
The other reason I wouldn't use Erlang is that Elixir has a much more vibrant & active community. A lot of the Erlang libraries (as of a few years ago when I last looked) were quite old & there wasn't a lot of active development being doing on them. I like being able to track down answers to questions & documentation that is more current. And of course there are more likely to be off the shelf Elixir libraries available for download, too.
The other reason I wouldn't use Erlang is that Elixir has a much more vibrant & active community. A lot of the Erlang libraries (as of a few years ago when I last looked) were quite old & there wasn't a lot of active development being doing on them. I like being able to track down answers to questions & documentation that is more current. And of course there are more likely to be off the shelf Elixir libraries available for download, too.