When comparing Reason ML vs V, the Slant community recommends Reason ML for most people. In the question“What are the best functional programming languages for programming beginners?” Reason ML is ranked 11th while V is ranked 19th.
Ranked in these QuestionsQuestion Ranking
Pro Superior type inference
Ocaml type inference is so smart that you never have to repeat yourself and keep code very clean, type errors also are very pleasant
Pro Immutability with escape hatches
reason includes true immutability, but it has escape hatches to let you use mutations in exceptional cases.
The same reasonml code can compile to js (eg. run on browsers or node.js, use any lib in npm), or compile to assembly thru ocaml (unless of course you load js externals), running on any device, with C-comparable (or better) performance.
Pro JSX syntax natively supoorted
reason was created by the creator of react, for developers already using JSX to template web or native UIs this results very familiar
Pro Fast as C
V is easier than C and fast like C.
V is simple and powerful.
V has generics.
Pro GUI editor
A visual editor for building native GUI apps is planned, it will use WinAPI/GDI+ on Windows, Cocoa on macOS. On Linux custom drawing is used.
Con A standard async syntax is pending
Async syntax is not standard across native/js projects and in both cases a bit awkward for non-ocaml devs. Currently this is reasonml most voted issue in their GitHub repo so hopefully, there's news soon.
Con Alpha stage
V 1.0 release is planned for December 2019.