C++ STL: Which method of iteration over a STL container is better?

Question

This may seem frivolous to some of you, but which of the following 2 methods of iteration over a STL container is better? Why?

Answer 1

The first version works with any container and so is more useful in template functions that take any container a s a parameter. It is also conceivably slightly more efficient, even for vectors.

The second version only works for vectors and other integer-indexed containers. It'd somewhat more idiomatic for those containers, will be easily understood by newcomers to C++, and is useful if you need to do something else with the index, which is not uncommon.

As usual, there is no simple "this one is better" answer, I'm afraid.