This question is related to, but not quite the same as, this question.
Are there any benefits to using std::vector instead of std::str
I think the only benefit you would gain from doing that would the ease of incrementing over the std::vector of characters, but even that can be done with an std::string.
You have to remember that even though std::string seems like an object, it can be accessed like an array, so even accessing specific parts of a string can be done without the use of a std::vector