When comparing PureScript vs Crystal, the Slant community recommends Crystal for most people. In the question“What programming language has the best syntax?” Crystal is ranked 3rd while PureScript is ranked 21st.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Higher kinded types
Has Typeclasses and RankNTypes

Pro High performance FFI code
The Eff monad, which is used for FFI code, optimizes out calls to bind, and supports tail call optimization, resulting in clean, efficient Javascript. The psc compiler also specifically recognizes the ST monad, and transforms scoped variables into mutable Javascript variables, for even more efficient code.
Pro Type safety
Compiling should be your first unit test. A tight type system (static and hopefully strong) will catch many logic errors that are often difficult to spot through debugging. In languages like PureScript, if it compiles, it often runs properly.
Pro Pure functional language
You cannot have side effects, unless a function is explicitly defined as so.
Pro Modules can be compiled to CommonJS
Modules compiled to CommonJS can be included with 'require', making it incredibly simple to call Purescript code from Javascript.
Pro Has row polymorphism and extensible effects
Pro FFI
FFI system is quite good and easy to use. You can import functions curried or not curried. Records and arrays use native JS objects and arrays.
Pro Thorough documentation
The Purescript website has fairly thorough documentation for all of the language's features, and the Purescript blog contains several examples of practical usage.
Pro Awesome web frameworks
Thermite (React)
Halogen (VDOM, similar to ELM)
And hit these up with Signals, Isolated/(Managed?) Components, powerful functions and FFI
Pro Elegant syntax as Ruby
Pro Fast performance
Pro Has co-routine
Pro Compiles to native binary
Cons
Con Lots of dependencies needed to get started
Purescript is written in Haskell, but meant to be used with Node.js. As a result, to get started , users must install ghc, cabal, node.js, grunt, and bower. Purescript also has its own compiler, and different semantics form Haskell, and so even after installing, there's still some overhead to getting productive with Purescript.
Con Lack of good IDE/tooling support
Con Documentation not updated
Con Ecosystem not stable
Con Restrictive FFI
Functions exported are all curried, and must be called as such from Javascript. The FFI syntax for importing Javascript functions, while slightly simpler and more readable than UHC/Fay's, means that calls to methods on objects must be wrapped to pass the object explicitly as a parameter.
Con Slow compilation
On large project, for example Halogen
Con Aruguably no better than a meme language
The elitest attitudes in the community are unwarrented. Not recommendable for production use. Poor error messages, odd compiler errors, poorly documented behavior, etc..
Con Small community
In regards to its age and already past 1.0, the community is still too small.
Con Not cross-platform
No official Windows support.
Con A language only Ruby fans can love
Ruby-ish language.
Con Slow compilation
Con No parallelism (yet)
Not actual anymore.
