C++ FileIO Copy -VS- System("cp file1.x file2.x)

Question

Would it be quicker/efficient to write a file copy routine or should I just execute a System call to cp?

(The file system could differ [nfs, local, reiser, etc], however

Answer 1

I would put my money on that the OS knows the most efficient way to copy file A to file B. The same applies for any api functions.