I think both are important. Use property-based tests to fuzz for mistakes you might have made. Use hardcoded value tests to ensure that common future breakages

I think both are important. Use property-based tests to fuzz for mistakes you might have made. Use hardcoded value tests to ensure that common future breakages of edge cases are caught, and to validate that your property-based tests are even doing anything. Usually, property-based tests are more complex, which means that the chance of an logic error in the test increases, and having something easy to verify hardcoded brings peace of mind.