You'd rather use a language full of undefined behavior as opposed to one in which (practically) every behavior of a program is specified by ECMA-262? To "avoid surprises at runtime"?

Surprises based on undefined behavior are usually not surprises at runtime, because of superior tooling. Either way, C is best because it has both of those things (tooling, defined behavior). It is possible to write very nice C.

> Surprises based on undefined behavior are usually not surprises at runtime, because of superior tooling.

Yes, they are. Empirically ([1], just to name one example).

> Either way, C is best because it has both of those things (tooling, defined behavior).

C has tons of undefined behavior.

[1]: https://lwn.net/Articles/342330/