Subjectively, I think PureScript is the better language (in terms of aesthetics and expressiveness) also it has overloads so (25) and (2.3 3.3) instead of OCaml's odd (2.3 *. 3.3).
Reason has a much faster compiler, efficient immutable operations, and is built using tried-and-true tech (OCaml).
I also really like PureScript, but the output from PureScript seems to be a lot larger than OCaml/BuckleScript and have worse performance. OCaml/BuckleScript has a really small stdlib that is lacking common functions, does not support type classes or point free style. A lot of groups end up making their own stdlib. BuckleScript is probably the more practical option at the moment.
Reason has a much faster compiler, efficient immutable operations, and is built using tried-and-true tech (OCaml).