Using STL algorithms, is it better to pass a function pointer or a functor?

Question

Which of these 2 methods is better and why?

Method 1:

void fun(int i) {
  //do stuff
}

...
for_each(a.begin(), a.end(), fun);

Method 2

Answer 1

#1 is simpler to declare the function
while #2 the functor looks more like a function call.

(Sometime you have to despair of c++ syntax)