In practice the multiple dispatch overhead is elided by the compiler. If it can’t be you’re doing something truly dynamic, which is generally unavoidably slower. It’s still a better place to be than everything being a generic Object type.

The nice thing about Cython is that you can have both - all the multiple dispatch you want with fused types, or escape that paradigm to do other things if you desire. It gives a lot of surgical control.

I don’t think that is true. As far as I know, Cython let’s you do function overloading and single dispatch via class inheritance. I think you also miss out on the type inference that lets you do things like pipe dual numbers through functions without any dispatch related overhead.