Question: I've been putting time into learning functional programming and I've come to the part where I want to start writing a project instead of just dabbling in tutorials/examples.

While doing my research, I've found that Erlang seems to be a pretty powerful when it comes to writing concurrent software (which is my goal), but resources and tools for development aren't as mature as Microsoft development products. 

F# can run on linux (Mono) so that requirement is met, but while looking around on the internet I cannot find any comparisons of F# vs Erlang. Right now, I am leaning towards Erlang just because it seems to have the most press, but I am curious if there is really any performance difference between the two systems. 

Since I am used to developing in .NET, I can probably get up to speed with F# a lot faster than Erlang, but I cannot find any resource to convince me that F# is just as scalable as Erlang. 

I am most interested in simulation, which is going to be firing a lot of quickly processed messages to persistent nodes.

If I have not done a good job with what I am trying to ask, please ask for more verification.

Answer: 
What do you mean by "viable?" "Having the most press" is not necessarily the best way to choose a language.

Erlang's claim to fame is its capability of massive parallelization. That's why it's commonly used in Ericsson phone switches. Erlang is soft-realtime, so you can make certain performance guarantees about it.

F# benefits from the optimization capabilities of the .NET Jitter. In addition, the language itself is designed to be a high-performing functional language (it being a variant of OCaml, widely used in the financial industry because of its speed).

Ultimately, unless you plan on running millions of tiny agents at the same time (which is what Erlang is optimized for), F# should be up to the task.

[This page](http://www.erlang.org/faq/introduction.html#id51928) explains the appropriate use cases for Erlang.
Few objective statements can be made on this subject because the performance of these two languages is strongly dependent upon the application and programming style.

The only advice I can give is that F# has the performance advantage of a static type system and the CLR does a good job leveraging this in order to improve performance. F# does have asynchronous agents and message passing but it has not been optimized and synchronous code is often over 10× faster.

Erlang is dynamically typed which puts its at a significant disadvantage in terms of performance (expect a lot more boxing) but it was built from the ground up to support fast message passing between asynchronous agents so that may well be a lot faster than the equivalent F#. However, I have no benchmark results to back this up: it is just my expectation.

As an aside, both Erlang and F# are relatively fringe languages with small communities and, due to their different target markets, people familiar with both are rare. The only person I can think of who nearly qualifies is [Jesper Louis Andersen](http://jlouisramblings.blogspot.com/) but I'm not sure how much F# he has done.