In STL maps, is it better to use map::insert than []?

map[key] = value;

using std::cout; using std::endl;
typedef std::map<int, std::string> MyMap;
MyMap map;
// ...
std::pair<MyMap::iterator, bool> res = map.insert(std::make_pair(key,value));
if ( ! res.second ) {
    cout << "key " <<  key << " already exists "
         << " with value " << (res.first)->second << endl;
} else {
    cout << "created key " << key << " with value " << value << endl;
}

using namespace std;
using namespace boost::assign; // bring 'map_list_of()' into scope

void something()
{
    map<int,int> my_map = map_list_of(1,2)(2,3)(3,4)(4,5)(5,6);
}