Indeed, fable is a very neat project, but to be honest, it is not as mature as BuckleScript at this time.

For example, it takes around 20~80ms to compile a single file for BuckleScript, while Fable would talk 10x more to compile.

Its generated code is pretty but its performance is not very good, see this issue (https://github.com/fable-compiler/Fable/issues/646) "this can make a difference in speed of up to about six or seven times for tight loop code using tuples, records, lists, unions, etc.(compared with BuckleScript)"

But Fable is a nice project, JavaScript platform is large enough to have both :-)