Faster in what? They both compile to IL code, and there execution speed is relatively the same, C# has it beat on somethings F# wins in others. Development wise, once you get used to it, I find it much faster. I have to write less code, and it's generally more correct the first time due to the rules it enforces.

I was about to mention perhaps they mean faster to write, and also conceptualise, but you nailed it. I find with F# that sure you are writing less actual code, like 1000 characters instead of 2000, but for me the biggest gains from using/thinking in a functional paradigm, and having access to functional tools is in the process of actually tackling problems. The conceptualisation, execution and testing of solutions for these problems for me has been less onerous and more enjoyable with F# than using C#.

I meant faster to actually program the tests, as you alluded to.