Thinking again, I think the first sample is more for specialized code, for generic code, for example a LogEvent method in your class, you need to open and close the file, and in that case StrToFile is not only a little bit faster (or let's say the same speed) but also more readable and less prone to error, for example in my first version when I moved the open and close inside the loop, I had forgotten fseek, which then did not write the file properly, as it kept overwriting it.