I did read the perlopentut and man pages for open and sysopen. And as jwkrahn mentioned, sysopen is equivalent to C's open, but I'm still not sure what situation is open better than sysopen.
That depends on your definition of better. Some people consider less typing for common situation to be better. Further more, there are things that can be done with open that cannot be done with sysopen. And there things that can be done with sysopen that cannot be done with open.