unique_ptr destructor advantage

What is the advantage of using the using a unique_ptr destructor over just closing the file directly in C++11?

i.e. this code

FILE* p = fopen("filename","r");
unique_ptr<FILE, int(*)(FILE*)> h(p, fclose);
if (fclose(h.release()) == 0)
    p = nullptr;

vs.

FILE* p = fopen("filename","r");
fclose(p)