F# is primarily functional, Scala is much more of a hybrid of both OO and FP; so Scala has things like traits that are actually advanced OOP constructs, while F# tries to push you more in the direction of pure FP.
The tradeoffs are different also. F# focuses a lot on performance in the spirit of Caml, whereas Scala is a bit more free to dive into more powerful features that go against that spirit. This is my grock at least of my conversations with Don and Martin over lunch when Don was doing his sabbatical at EFPL.
Case in point, .NET already has FunScript, an F#-to-JS compiler: http://funscript.info/
FunScript also provides a way to do strongly-typed interop with TypeScript, via F#'s type providers.