Uni vs Multy

Unityped languages: Making mistakes ist verboten. Any and all of human type errors will be manifest as late as possible, in the most unconvenient way. This is our way of disciplining the Untermensch. Also, you are responsible for any and all code refactorings. The only form of correctness assurance available to you is testing, even though it can never prove the absence of errors. Heil Dynamic! Unityping uber alles!

Multityped languages: Hey, I know you make mistakes, buddy. We all do, we're human, after all. That's why we made this type system for you. Now the compiler can be your buddy, it will get your back and catch most of your errors for you as early and quick as possible! And if you want to refactor something, it will help you out by pointing out the things you missed real quickly. Now you can eliminate most errors without even needing to run your program - how fast is that? And the type system will actually eliminate these errors, as in prove their absence! Now you'll have to do 3 times less testing! Just helping you out, bro.

A program that fails from an error that was handled as an exception with no reasonable recovery behavior is just slightly better than a c program that crashed from a segfault. It might not be vulnerable to buffer overrun attacks, but it is still vulnerable to denial of service. And if it's operating the fuel control of a rocket, it's going to malfunction if it encounters the exception again every time it tries to recover, costing money and possibly lives. Your type systems are puny. They speed development, but they do little for safety.