I'd pick Balance is key, as it feels like a project's goals and constraints dictate the right trade-off between readability and performance.

I'd say 'Balance is key' - in my experience, a readable codebase can save hours of debugging time down the line, but there are cases where a performance-critical section needs to be optimized.

I'd say 'Balance is key' - there are cases where performance is critical, but readable code saves us in the long run when maintenance is needed.

I'd go with 'Balance is key' - in my experience, a readable codebase that's slightly slower is easier to maintain and debug than a highly optimized but convoluted one