if the sub runs to 20-30 lines, I'd rather have the header

Obviously if it works for you...

However, if it were me and the sub ran to 20-30 lines that I couldn't understand without half a dozen lines of comments I'd refactor it into a larger number of smaller subs - each of which I could understand without half a dozen lines of comments.

I doing code maintenance I tend to ignore comments, since I find that they're out-of-sync with the code half of the time.