When comparing Chicken vs Hy, the Slant community recommends Chicken for most people. In the question“What are the best Lisp dialects?” Chicken is ranked 5th while Hy is ranked 8th. The most important reason people chose Chicken is:
Chicken has easy to navigate and understand [documentation](http://wiki.call-cc.org/man/4/The%20User%27s%20Manual) that's updated frequently.
Ranked in these QuestionsQuestion Ranking
Pro Well documented
Chicken has easy to navigate and understand documentation that's updated frequently.
Pro Friendly, welcoming community
The Chicken community is very helpful and friendly.
Pro Easy to embed
Likewise, FFI is very simple compared to most Scheme implementations.
Pro Compiles to native code
Pro Permissive BSD License
It has a tool named chicken-doc. With its help you can easily add autocomplete and documentation features to your favorite editor.
Pro Python interop
Hy compiles to Python's abstract syntax trees. Python can import Hy modules, and Hy can import Python modules.
Pro Easier to read
Distinguished between arrays (or vectors) and function calls by using  and (), respectively.
Pro Copyfree and open source
Uses the MIT (expat) license.
Con Lacks proper UTF-8 support
For more detail see http://bugs.call-cc.org/ticket/1374
It's been up there for 9 months, still not fixed.
Con Lacks numeric tower support
The core system currently does not support the full numeric tower. However, there is an extension library available.