If you are writing general purpose software, I would suggest Rust if I have nothing else to go on, although there are plenty of other good choices if you know more about the problem.
In a few cases there is today a special purpose language for the kind of thing you're writing which will knock both C and Rust on their backs for performance because it was never trying to do anything else.
I think C is still a good choice for the following reasons:
- Performance is generally very good and while special languages can sometimes be better it usually easily possible to get the C code to the same level.
- But with special languages you will often run into limitations where you are stuck.
- It has long term stability
- Compile-times are short which I really like
- There are good tools
- It has very good interoperability with everything
- The code an easily be reused from most other languages, so it does not tie you into a specific framework
- etc..
In a few cases there is today a special purpose language for the kind of thing you're writing which will knock both C and Rust on their backs for performance because it was never trying to do anything else.